Further to what @eatstoomuchjam said, I think there are only three types of performance:
it can't play ungraded footage realtime (ie, you can't edit with it)
it can play footage realtime but can't do it with a heavy grade (ie, you can do some colour grading realtime)
it can play footage realtime with a heavy grade (ie, it's reliable and you can colour grade live in front of a client)
The spec required for level 2 should be researchable and BM would have made this pretty efficient I would imagine. The spec for level 3 is a "how long is a piece of string" question, depending on a ton of variables including timeline resolution and only you can answer it, but if you're going to be doing lots of heavy things like NR and spatial treatments on a 4K timeline then you're probably well into Ultra / Studio territory.