A:AnswerI'm not sure of the answer, but you could always save your stuff on your actual computer drive, and then it wouldn't matter if it changed your One Drive storage.
A:AnswerDownload the suite on you phone and use the same credentials as the computer or key and it will populate
Make sure the suite has the capability for multiple devices
A:AnswerMy advice - Keep your office 2019. The files are backward compatible, and unless you're at the super-expert level, you won't notice a difference. Office also probably includes more programs than Personal 365.