M2U can do Public Mutual?

No difference as you use PMO or PBeBanking.

SC is still the same.

Do you have PMO access?

If yes, why don't use that and pay using FPX with M2U? 

AFAIK, Public Mutual Funds is only distributed by Public Mutual, while funds (those funds which begins with "PB" in their names) issued by Public Bank can only be bought in Public Bank.
PMO is Public Mutual Online. It is their online system where registered members can do various types of transactions, except for purchasing funds under EPF withdrawal scheme.

To register as a member, you must first need to be a registered investor with either Public Mutual or Public Bank. Meaning you must initiate a face-to-face contact with an agent from Public Mutual or go to a Public Bank branch and purchase your first fund.

PMO distributes both the funds from Public Mutual and Public Bank. If I'm not mistaken, you can also do transactions on those PRS funds from Public Mutual.