In my opinion no. The fundamentals of OS X aka macOS have not changed significantly since 10.3. features that were slow in old versions are still slow in the newest new. But you should know how to do clean install macos monterey correctly. This guide will help you to succeed and improve your computer performance.

No. It’s mostly only Windows PCs that suffers from that kinda degradation - mostly. I’m currently replying to your question on a MacBook Air 2017 and I will definitely upgrade from Big Sur to Monterey because I want all the new functions.