And if you had 32GB of RAM it would be using 24GB and you would be saying 32GB of RAM is a no brainer. macOS uses what it finds.Just got my M1 Mac Mini this week. Use it for FCPX And Logic Pro. 16 GB RAM 1TB storage.
Using FCPX uses 12 GB RAM average.. It is a no brainer about RAM.
Memory Pressure is what matters.
I am not saying 16GB is not beneficial for your requirements and criteria, just that the amount of RAM used is not the way to tell.
An uninformed user would misinterpret your post as meaning FCPX can't be used with 8GB of RAM, which is not true. It might take a bit longer which might be important for you, but not matter at all for an average user.