I'm going to regret all the following.

1) You have an extensive amount of experience, so you should know that individual requirements between users and administrators differ, and no one person can give you a configuration suggestion based on the information you gave. I don't want to sound like a dick (but I will), but you have twenty years of experience, so you should know what you need, what your options are and how to find out the things you don't know. Asking someone else to give you advice on an individual use-case basis, when it's largely requirement and preference based, is pointless, especially if you know what you're doing. You'll just end up rubbishing their suggestion or bringing another factor into it which you didn't mention, and wasting both your time. Your best option is to try what you know and see if it works. The answers that work for Linux4Noobs are "Ubuntu" and "Mint", but for someone with more Linux experience than the total length of time I've been in both industry and education, the answer is you have to find out for yourself. Personally, I don't know how you could administer servers for 20 years, develop for them, and not have faced this problem years ago. Leaving name changes aside, you've been using a Red Hat version since about a year after Marc Ewing released a public version of RHL, or Debian since around version 1.0. You must have seen an incredible amount of changes and accumulated a vast amount of experience, so I'm incredulous that you need to ask a pretty minor subreddit for advice on how you should set things up.

2) You need to change DPI settings on the desktop, and sometimes in different applications. This is one of the first Google results for HiDPI, which tells you how to do that on a variety of desktops and applications.

3) Yes, dual boot Windows. That is how you play games. Unless you have a specific set of games you want to play that either run natively or will run through Wine, you will spend more time trying to get games to work than actually playing games. I can get back into Linux from Windows in about 15 seconds with an SSD, so I have no idea what reasonably quickly means to you.