TMC2209 produce less heat than TMC2208 due to lower on-resistance MOSFETs. Especially on step sticks with such limited ability to carry away heat, I’d suggest the 2209s instead. They are only a few $$ more and less likely to cook themselves.
You’ll want to get TMC stepsticks that put the chip on the bottom side of the board and the heat sink on the top, with plenty of vias to carry heat through. You don’t want the heat sink attached to the IC case because that doesn’t conduct heat as well.