Tom

A question with no right answer, because it is a matter of taste and habits.

Both are very much sophisticated desktop environments which very useful defaults. Neither Gnome nor Plasma are too complicated for beginners and can be customized easily. If you want to you can go very deep into the customization too.

A combination of different.

For brainstorming Logseq is great, for tasks I use CalDAV in combination with Thunderbird and JTX Board (Android) a lot.

What if you are using VIM and Arch …

That after getting used to Linux I will hate to be forced to use less free operating systems.