The XFce version of Linux Mint is not the same as the default XFce. It's been modified to look like the default Cinnamon Linux Mint. You can't tell them apart most of the time, so it doesn't look retro. At 600 points of cpu, xfce can run well, and work better than Lubuntu. Lubuntu is great for less than 400 points cpu, but if you have more than that, you are wasting your user experience (the xfce linux mint edition is much better than lubuntu's in user experience).
I suggest you don't disable flatpaks, you just disable it from the menu so it's not visible to be clicked. But let it in, just in case it's needed. Right click on the cinnamenu (if you install that), open preferences, and then open menu editor. There, you can make the flatpack menu entry invisible.
Yep, I run these, especially since I have a couple of raspberry pis, that you can't do without these.