Progress. The trashcan's extreme white to black was in fact a lightmap issue. The lightmap index was set to the wrong number without me knowing it or where the switcher was. Now the fish's uv seams are still there though as well as a slight seam on the trashcan which might be because of the model (I'll look into that). I'm…
I used it like that a long time ago : default max keys, middle click on the low rocker, right click on the high rocker. However I strongly suggest you to pick up DRaster Switcher for Max, to bring in Maya controls. They are better overall, and much more tablet friendly too. (same rocker configuration as above)
it depends on the original skeleton joint orientation; controller rotation when it was connected to the skeleton; orientation of the intermediate objects like space switchers, roll joints, etc, plus any constraint offsets, then on top of that there's rotation order. and rigger preference/habits. just something animator…