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).