Homebrew maintainer here. We don’t officially support Big Sur yet, but installing it via Rosetta will cause it to fetch x86 bottles instead of ARM ones. At least, that’s the plan.
Are these 'good practices' for Arm Macs?:
1) When spinning up an iTerm session, figure out if it's 'Darwin x86_64' or 'Darwin arm64' - and configure paths accordingly. so they use the right brew binaries.
2) Easily double check what version of a running package/keg based on what arch is displayed in Activity Monitor.
3) That way, you can just use brew with Rosetta to start (which I did) then build up native arm Brew over time. and let the Rosetta brew fall away.