Can I feed 2 sub-panels off one breaker?
Since this is fed from a breaker in your main you can do it with both wiring methods but it would be considered a feeder and the wire size would need to be good for 125% of the breaker or 125A the way I interpret the code. If all the loads are non continuous it could be 100% but with all those spaces there will probably be a few continuous loads so better to be safe for the long run.