Oh, good point. Yes, my resolution is 2256x1504 and found the 1x too small so I have to scale it up. I haven't had any issues but I also typically do lower level and back end type work (occasional front end when needed). I also haven't done any gaming with the laptop (except some minor experimentation with Godot). If you are a designer or serious artist I recommend at least trying out your os with fractional scaling first.
I run at 2x scaling and then set the text scaling factor to .85, so the effective text scaling becomes 1.7, and I avoid the issues with non-integer scaling in Wayland.
Yes, using the tweak tool. I believe there were also a few apps I had to tweak separately, like setting the default zoom level in Firefox. As for external displays, I don't generally connect my laptop to one, since my displays are connected to the desktop PC that I also own (which I run at 150% scaling in X11 mode so that fractional scaling actually looks good).