The 180 is the ttsx. Tipped version. The 200 tsx is deadly pushed at 2600 ish and is shorter to allow for magazine length restrictions. Personally I prefer the tsx.
I can't speak to the 180 TTSX but I have run the 200 TTSX in both the .358 and the 35 Whelen AI.
2600 FPS is selling the 200 short in both. 51/TAC gives me 2700 FPS in the .358 (Savage 99) and 68/Varmint gives about 2975 FPS in the WAI (98 Mauser). NOTE: My calculations indicated 67/Varmint would be max in the basic Whelen with a 200 grain. My AI needed and extra grain to get the same velocity.
I would expect the 180 TTSX to hit at least 3100 with appropriate powder. Speer publishes 3172 FPS with 70.0/Varmint with their 180 HotCor. That's impressive!
