Command line is a lot more powerful for a lot of cases. Most CLI programs are written with the idea that the caller might be another program, so they tend to be easy to chain with pipes and redirection. So you have tons of simple tools that you can combine however you need.
I generally aim newbies at Mint, but ubuntu derived distros are pretty easy and stuff often 'just works'. That's why my daily driver is xubuntu.
All over the place, really. Another advantage of ubuntu derived distros is you'll find a lot of the tutorials and stuff will assume you're using ubuntu. I just hit a search engine if I need help with something.
I've journalled for a few years in the form of a bunch of markdown files. Occasionally I'll read back or search for things to help remember things I'm not recalling clearly.
Using Obsidian with mega on desktop and FolderSync covering syncing the android side of it. Works fine.