I’ve used a cheap 3D pen to weld smaller prints together. Works pretty well. You have to be quick because once the filament starts to cool it doesn’t bind well. It also doesn’t look that pretty, but I only use it in areas that aren’t visible in the finished product. If you’re planning on sanding it after I think you’d be fine.

Have you considered a Prusa Mini? Unless you need a larger print bed, it’s a great starter printer at that price point.

I have a MK3S and a MK3S+, one with a stock nozzle and one with a Revo. I print the same gcode on both machines and haven’t seen a need to tweak the settings for the Revo. Have you tried slicing with the default settings for Prusament PETG in Prusaslicer?