I personally use eco earth for all my T's. Peat moss is fine also but I just don't personally like it. No need really in mixing the two though IMO.
This has nothing to do with the OBT and just me rambling: If you wanted more humidity you could mix vermiculite with either the eco earth or peat moss. I have tried that too a few times (not with my OBT) and didn't like doing that either really and always ended up switching back to just straight up eco earth. The straight up room humidity the T's are in now is reading 73-75%. I never have an issue with humidity really except for maybe in the winter. I have too keep an eye out for mold because of the humidity.