You do not need the PX1 if you are update running the executables from page 1.
But I don't know why they remove the original bioses from page one (the pre bar bioses with the stock pl ) it would be nice to have them all in one place. Know I don know where to find them .
Also 0% fans not possible with switch on OC position with stock or XOC or XOC BAR
Actually the OC position means just disable fan stop.
Maybe there are some bugs with other bioses too not going in 0 % fans but don't know