I think this will benefit fighter pay overall. It's going to create more transparency with UFC income, viewership, and fighter income.
It's going to screw over the fighters headlining cards though. All of the existing contracts with headline-level fighters are based on PPV points + base salary. Now there will be no more PPV points. So everyone at the top immediately starts making less. This will necessitate either 1) contracts to be re-made for the new model, or 2) the UFC will have to offer some per-view bonus for CBS/paramount+ viewer numbers (i.e. $2 per view, so if you draw 5 million views on paramount+, you get $10 million).
This actually would make sense, because there will still be unskippable ads embedded within the stream (between fights, etc.). That means the UFC/CBS could be sharing substantial ad revenue still, if the UFC viewership numbers get big enough.