So for example, the 三国 kingdom of 魏 is spelled ㄨㄟ because ⟨wei⟩ is (nothing)+uei

yeah, so one of the differences is that bopomofo never abbreviates a syllable, so ⟨hui⟩ sounds like h+uei, which becomes ㄏㄨㄟ h+u+ei

yeah! predictive text is similar to pinyin input, e.g., if you type something "bb" and get 爸爸, you can do ㄅㄅ to get the same result
for the consonants, it should be a 1:1 match with pinyin but the remainder of the syllable are a bit different; I might be a bit weird but I had fun learning bopomofo 😇

Sorry if you have already settled on what to do, but in case it helps anyone else: Pinyin is the last keyboard for TC (TW) on Gboard or you can swap a SC to TC from settings ~

The only response now is to make a pillar of Roman letters in the museum of English characters 😈

the tree of shared characters between China, Japan, and Korea was also very cute