The TM:EX = R:EX = 10:EX all the same ski, just different marketing spin. For touring many people your weight like something in a 180cm to 185cm for the fatter boards around. BD/Atomics are decent planks, so are K2s, so are most skis made to today - buy something cheap this summer, if you hate it you can resell it come winter for as much or more than you paid for it.
Whats the difference between AT and Downhill? Depends on the skis. For some its a different topsheet (see above Atomics) for others they've lightened the weight. As for "compromising performance" all depends on what performance you want. Everythings a compromise from 220cmDH boards