R/S and R/Wn aren't Tp intensive, you can cover both combos with a minimum of 120 ish tp. I'm at 190m so I have some luxuries. But 120 will still do a great job.
Wn/s is just another class primary where you get tp for ur main. It's not that you can swap back and forth, it's more so if you wanted to do something else in a new chapter then you still have options. It's actually pretty light in the tp department compared to other combos. Finally, all 3 combos are top 6 dps. If one gets nerfed, you've still got 2 others