I was taught it was "BOW-ba" or "BOH-ba", but AI actually linked a number of studies that seems to confirm it is supposed to be and usually is "BOO-ba" (i.e. bulging eyes Pepe) in experiments. I don't personally think either pronunciation would change the results though.

The strange spelling is partly intentional to make sure that people read it as a very fake word with no known definition. In English bow, boba, boob are all real words.

Because English is the odd one out with the non-obvious mapping of sounds to character.