TSA-HND on NH is operated by secondary NH aircraft (Normally ANA subsidiary Air Japan- NOT Japan Airlines before someone tries to correct me). Their aircraft are not the best config compared to other NH aircraft. However until we see EVA join Star (hopefully) Tokyo Haneda to Taipei Songshan - your only Star Alliance choice will be on ANA with the Air Japan aircraft
Back to the OP: Agree TPE - NRT is pretty bad in Y; it's just as bad in C with the older 777's in use. If you don't mind earning to a OneWorld FFP then I suggest doing the Cathay Pacific flights from TPE to NRT (CX has historical route authority from TPE to a few destinations other than HKG). A lot of Y on UA TPE-NRT is agency booked tickets in Taiwan or Japan ; the connecting traffic does exist on that route but there are a lot of people on the TPE-NRT UA route who are purely going between Taiwan and Japan.