Linux
looks like you have already tried and can't find one that works for you out of the box.
there are many different GUIs for Linux that you can customize to your hearts content. at the very least, you don't have an entity aggressively trying to remove your customization's.
one thing that i didn't see you show from the Linux crowd is tiling window managers.
they don't really solve the same problems you are complaining about here, but the main idea is to remove needless effort organizing your windows. unfortunately, from what i have seen most of them rely on you searching for the program you want. admittedly, it's also what i do these days. the windows 10 search is abysmal - you can literally type the exact name of the program, respecting case and the beset match will be to search the web.
Unfortunately, if you switch to Linux, you'll still have to boot windows to play a large chunk of your games. it should improve your workflow for the parts where you don't have to run games though. I guess it'd suck if you have to quickly boot a game to get a clip of something.
One place i found for nice looking UIs: https://www.reddit.com/r/unixporn/
In my browsing of it, seemed to be more style than functionality. I guess pretty == upvotes. There are many low-contrast themes. But on occasion there seems to be something that looks useful.
Edit: just found this, seems to be addressing my exact complaint: https://www.reddit.com/r/UsabilityPorn/
My Workflow basically a rant
I take refuge in my terminal... thankfully there isn't much I need to do that isn't in the browser or the terminal.
I agree with the points you make about the terminal, it doesn't work for a large majority of things. but for the specific things i need to do for my job, it works well.
My current job has me working on a mac, and the keybindings are different... Obvious ones like ctrl+c etc, but also things like the home & end buttons just don't work in most programs on mac (or if they do, they'll take you to the start of the text instead of the start of the line).
or Firefox, where on windows & Linux ctrl+h will bring up history... on mac you use the command key instead (ctrl button is there but seems to just be vestigial), which works for most of the hotkeys in Firefox except history because command+h hides your window.
I dread the day that I have to work on Windows, because from what I have used, the terminals on there aren't great. Sure you can get bash on it, but you still run into random problems.
your hand-on-mouse-at-all-times theory is interesting... in my editor the philosophy is the opposite. you should be keeping both hands on the home-row at all times. same concept, but yours makes more sense for video editing and the like.
P.S. the magic mouse is terrible. No middle click, no right click by default (although you can enable it). Really the only 'gesture' I found useful was a glorified scroll-wheel, although I didn't go to town customizing different actions. Oh, and it would screw up those 3 simple gestures too often to tolerate. To top it all off they put the charging port on the bottom of the mouse so you can't charge it and use it at the same time. Talk about UX.