Would like suggestions for  anti-tilt (?) followers and magazine springs for the Brownell AR15 20 rnd magazines.

Apparently Wolffe is the way to go for springs.

I was thinking of MagPul followers (20 round magazine) BUT I now read that they are ONLY for curved magazines. Didn't know curved 20 round magazines exist.

Thoughts?

I don't need to put 20 rounds in the magazine. 8 is the most as I am using the magazines in NRA/CMP High Power "events".

If you don't care about getting 20 rounds in the magazine, you can put a MagPul follower in a straight 20 round magazine.
It will hold 16 or 17 rounds because the MagPul follower is taller than the standard follower.

D&H Tactical makes a curved aluminum 20 round mag that has a MagPul follower.
The mag body is about 1/2 inch taller than the classic straight 20 rounders.

In general, anti-tilt followers are more critical in 30 and 40 round curved mags.

Never had any trouble with the standard metal followers on straight mil surp 20's. As mentioned above, it's generally the 30's that have trouble without a non tilt follower. If you're having trouble though, you could always use a dremel to buzz off part of a magpul 30rd follower. I did that for a cheap aftermarket 20 I had years ago. It worked fine.