How do I know what the final koopa will do in 8-2? I have been just jumping on the block and just hoping he doesnt hit me. Is there any way to tell earlier on in the level to see what he will do?

It's frame rule (as well as level speed within the frame rule) dependent. There are 3 things they can do. Dumb, low, and high. In all three cases you start your jump at the same point and then either hold jump to bop the Koopa or go under. The gif thread has all three combos and how to "defeat" https://www.speedrun.com/smb1/thread/uz8f3

Basically I just assume that it's either dumb Koopa or low... The one you can jump on top of. To me the "high" one looks too much like the low one to tell the difference, so I just die when I encounter it. At least anecdotally though (fortunately) the worst Koopa (high) seems to happen less often than the other two

I just jump on the stair and hope I don't die, I don't really see any difference. But it won't be a problem anymore if you go for BBG Kappa