Hi. I didn’t make switching UVs an option out of the box as I found most materials just use UV0 for their textures, but it shouldn’t be hard to change if you want to use UV1 channel. If you go to TexturePaintChamp->Materials->BrushMaterials you’ll see a handful of materials. You can open these up and change the TexCoord nodes to 1 instead of 0. The brush estimator material is the preview you see of the brush (so where you know where to paint). The materials with proxy in the name are the preview materials when you are adjusting your settings and the other materials are the actual output materials that will be used.
TPC uses the built in first person controls / mouse to move the camera around so you paint what you see. To have the screen static and cam rotation done on middle mouse would require a complete rebuild of TPC. Maybe I’ll update it one day to have this option, but it’s a lot of work so not currently something I’m planning on doing. Quixel Mixer is free and paints via a static view though if you prefer that.