Does installing Big Sur in an iMac 2017 affect my Final Cut ProX or iMivie?

(You may have to update to FCP 10.5, or should.) Scratch that, I see that Tom has already said 10.4.10 will work.

Don't forget:

a) do not upgrade mid-project;

b) MOST IMPORTANT - do not upgrade without a solid BACKUP

Just a note on "Big Sur or not".

Normally people have not installed a "FCP(X) only" but a "FCP(X) system" – this means plugins and apps around FCP to make it work the they like and love.

This "ecosystem" is sensitive to many small parts. So the question should be:

"Does installing Big Sur in an iMac 2017 affect my Final Cut ProX or iMovie ecosystem?"

The latter can hardly be answered without knowing details.

Questions like: "Will plugin X from vendor Y will work?" are essential.

"Spend 50 bucks for an external boot drive, backup your libraries, be aware that TimeMachine on Big Sur will be different…" is a good start for thoughts – I think.

I don’t know. Which versions do you have?

Yes. They work. You don’t have to update to FCP 10.5.