Re: 284 winchester
SAMMI spec is about the same for COAL. So, your magazine should be fine.
284 Win is often used for f-class. So, I would think it'd be a good choice for long range targets and mid range hunting.
good bullet selection
good barrel life
lower MV than other 7mm's
no lapua brass
Not sure why 22 MOA matters. Mount a 20 MOA rail with good glass and you'll have no problems getting to 1k.
3100fps sounds overly optimistic. If that's important, you might want to look at the 7mm SAUM or 7 WSM. But, you'll have to open up the bolt face. And, you'll probably need to single feed or go to a long action. That's especially true if you go to the big 7's.
A lot depends on whether you're using it for recreational targets, competition, or hunting.