It seems the OP is doing SFO-ICN-TPE and return and ICN-TPE on TG.
The US rule, as I understand it, is based on the first marketingcarrier, not operating carrier. So, in theory it will be 3x70 lbs since OP is Platinum.
The allowances are supposed to be attached to the eticket images - just like the old ALLOW fields on the ticket. So, theoretically, all the airlines should be able to see it. What I am not sure is that how the *A Gold extra allowances (i.e. 70 lbs intead of 50 and 1 extra piece) are handled with the eticket information.