1. I don't got it this: If you have a huge monitor why you need to have a double size fonts and icons?
When I buy a bigger monitor was for to see more information on that not the same but bigger. If so I use zoom or batter eyes glasses.
It doesn't matter!
2. On defaults it have to look like this (metal and nimbus):
On macOS it looks similar (not exactly) as Nimbus.
If under FlatDarkLaf or other LaF don't look OK (columns wide, fonts, borders, icons size etc) I suspect it is the fault of LaF not of the applications.
I think (rarely) it is easiest to correct the theme than to modify 100+ applications.
No offense, it is only my wrong opinion.