So delighted that you've been enjoying your first year of fellowship on FPN, and I hope you fall in love with your 3776 Chartres -- as I have with mine. Platinum makes some outstanding pens and, while they're not cheap, they're high on my list for most-writing-pleasure-per-dollar-spent.
A few thoughts to add to the many excellent suggestions and observations you've already received. I'm not including writing samples, but you might have a lot of fun looking through the beautiful stuff on the Stub o' The Day thread. Lots of modern and vintage examples, there.
I've been using/collecting stubs, CIs, and music nibs (plus a few obliques) in all price ranges for about 20 years. I get excited about them. I don't have as much expertise as many others on the board, but I do have a lot of experience writing with these nibs, both contemporary and vintage.
Firstly, the distinction between a stub and a CI is -- if not theoretically, then practically -- very subjective. The nibs.com article you've already been pointed to can make it seem like these are two very different types of nibs. But, in my experience, it's a continuum, with a lot of overlap between what one person calls a CI and another person calls a stub. You can get a pretty sharp/crisp stub, and you can get a pretty soft CI. A lot depends on who's doing the grinding. There is a thread on here (that I can't locate just at the moment) with considerable discussion of how the different nib-meisters' grinds compare. For example, without specific instruction, John Mottishaw -- who's amazing -- cuts the edges of his stubs a little too sharply for my tastes. Pendleton Brown has a softer touch. Richard Binder always struck me as right in the middle. Of course, all these folks will grind a nib to your specific request. But to make such a request, you have to know both what you like, and what their baseline/default is -- so you can ask them to vary from it. This isn't as difficult as it sounds, because you don't have to be able to describe the nib, per se; you can describe how you want it to feel, and what you want it to do.
(While stubs and CIs can be hard to distinguish from each other, and arguments might break out at the pen club about whether a nib is one or the other, music nibs and obliques are another matter. You can't mistake a proper, three-tine music nib for anything else, and obliques are also usually pretty obvious.)
Next: I haven't read, on this thread, anyone enquiring about what you'll be using the pen for. The practical distinction between stubs and CIs intersects with the type of writing you'll be doing and how you want the nib to perform. There are many types of lettering projects for which the sharp, crisp lines of a CI are really required to get the best effect -- not just maximum line variation, but maximum bifurcation between the down-strokes and cross-strokes (verticals and horizontals) without much middle ground between them. Conversely, if what you want is a comfortable writing experience, stubs are more likely to deliver that, with (ostensibly) more modest line variation, but with more fluid/rounded transitions between verticals and horizontals -- which may or may not be to your taste. When I started out on this odyssey, I wanted maximum line variation, so gravitated to CIs. I quickly found that, for my application, which is writing at length, CIs were a terrible choice for me. The ones I used delivered stunning line variation, but I couldn't write fluidly and quickly in a way that was comfortable. Those sharp edges kept catching, or I'd get "skipping" -- which was really not skipping, but the result of inattentiveness to nib orientation, to which CIs are more sensitive than stubs. So, I eventually settled on stubs for my application. They deliver the maximum line variation while still giving me a fluid handwriting experience. YMMV. Another rule of thumb is that the broader the CI/stubbed nib, the more sensitive to rotation it will be.
I have found that pens with stubs and CIs more often give me ink-flow issues than other pens. There is no reasons why this *should* be, but there are a couple of reasons why it happens in practice. First, there's that issue of nib position. Stubs and CIs can seem to have skipping problems even when there's no issue with ink flow, because some of these nibs can be particularly picky about how they're positioned on the page. The sweet spot can be tiny, and can require very specific angle or rotation. For me, the holy grail is a nib with a huge sweet spot and great line variation. This will remain mostly a fantasy, as the two are a trade-off. The second reason some stubs/CIs present flow challenges has to do with the amount of ink required by the broader surface contact of nib on page. A thick line requires more ink than a thin line, and some feeds aren't up to the job. This can be an issue with broader/wider stubs and CIs. In actuality, this isn't usually a problem, but I have seen it -- probably because I love broad stubs, and my tastes run to a really juicy flow. I can make an otherwise respectable feed beg for mercy.
I'm sure you already know this, but I haven't seen much comment about it on the thread: If line variation is what you're after, then you're going to get a lot more of it with a broader nib than a finer one. I have a bunch of medium-nibbed pens that I've had ground to stubs. I appreciate the subtle line variation, but I doubt many other eyes would even notice. Folks who get F nibs stubbed baffle me, but more power to 'em. You really start to see drama when you stub a B or a BB nib. It was being impressed with the visual impact from those nibs that led me down the path of music nibs. God help me. That's a whole 'nother thread.
Another note on line variation -- and, again, this is probably obvious and I don't mean to sound remedial...just for completeness and in case a newb happens upon this thread: You didn't say your quest was for maximum line variation, but by far the gold standard approach for line variation is flex nibs. I am not particularly a flex fetishist, but most of the lettering that leaves me awed is done with flex -- and a lot with flex nibs on dip pens. And that invites a discussion of flexy stubs, but let's not.
Lastly, it probably goes without saying that price is no indicator of the quality of a stub/CI -- whether factory or custom-ground. Don't let anyone tell you otherwise. I've had steel factory stubs that could write rings around some of my custom-ground gold stubs. Better put: I've had singing angels on both ends of the price spectrum, and I've had sweary miscreants (fit for nothing more than tormenting one's enemies) at both ends, as well. Had I to do it all again, I'd start by exhausting all the possibilities at the cheap end of the spectrum before investing in custom grinds on nice pens. I'm talking things like Nemosine, TWSBI, Lamy (and others), plus the aftermarket stubs like the ones you can find at Goulet, which fit a variety of modestly-priced pens -- including some of the Chinese and Indian cheapies.
As for obliques: Again, others are more qualified than I am to address the magic of obliques, but I've never found a job an oblique could do that a stub couldn't do just as well. The question -- at least in my hand -- is about how one holds a pen, by default. An oblique can provide line variation, but the job it's uniquely suited to is compensating for idiosyncratic rotation and nib position. For a long time, when I was a yoot, I thought I had to have oblique nibs because I'm a lefty. Pish-tosh. Now, one of my favourite pens is an oblique, but that's just a coincidence. I didn't pursue it with an oblique; it just came that way, second-hand. I'd like it just as much if it were a straight-cut med stub.
Holy cannoli this has been a long post. Apologies. The only other thing that comes to mind is this: I'm someone who normally likes certainties, precision, universal standards and rules. I like the idea of being able to know, without handling it, what the difference will be between a 0.8 CI and a 1.1 stub. In my experience, you can't. You've got to write with the buggers to know much at all about what the nib actually delivers. And you've got to do it with your ink and your paper. It's a freakin' stew; even if you think you know what's in there, you've got to taste it.
Have fun tasting.