I have a heavily modified CR-10. The most noticeable difference is going to be the complete structure change. I wanted to have an "all-in-one" printer, and decided to have some LEDs thrown in there to spice it up a bit. I've also added a TinyMachine's polypropylene build plate, which has helped my adhesion a ton. I needed to add an auto leveler to my extruder. Unfortunately, this printer hasn't been all perfect. The extruder gets clogged up if I don't change out the filament without extruding some of it first. For finishing, I typically do a few rounds of sandpaper, but have found that a Dremel is perfect for getting into small details. For slicing, I typically use simplify3d, Cura was just not working for me. I mostly use Inland PETG filament, but also really like the Amazon basics PETG filament. I've linked below all of the mods I can think of. If there are any more, I'll make sure to add them.
Simplify 3D - https://www.simplify3d.com
Dremel "pen" attachment - https://www.amazon.com/gp/product/B0000302Y8/