Will Macbook Air 2017 benefit from Catalina upgrade? I'm running Mojave on my Macbook Air (2017) and was wondering if anyone can recommend (or not) upgrading to Catalina now that 10.15.7 seems to be stable release.
I'm not using any 32bit apps, so no problems there.
However, is it worth actually upgrading? I know I can't use certain features (such as the battery health or sidecar), but should I do it for security, etc?
What are the experiences of other MBA 2017 owners after upgrade? Has anyone experienced slowdowns? Is anything actually better? Or should I just stick with Good Ol' Mojave?
Thanks.
However, is it worth actually upgrading?

A newer macOS release always includes the latest security patches for any discovered hardware of software vulnerabilities. So generally speaking, it's a good idea to upgrade if your device supports running it, given you have no reason to refrain from upgrading.

I know I can't use certain features (such as the battery health or sidecar), but should I do it for security, etc?

Yes.

What are the experiences of other MBA 2017 owners after upgrade? Has anyone experienced slowdowns? Is anything actually better? Or should I just stick with Good Ol' Mojave?

This experience could be pretty subjective depending on the apps being used, but generally speaking, a newer release of macOS also often includes under the hood performance improvements which are also claimed about by Apple.