The Studio will be my first M1 model and it sounds like all current M1, Pro, Max computers have slower USB 3.1 read/write speeds than Intel Macs, even on the latest OS. Maybe because Apple's custom TB4/USB4 controller chips are targeting TB4/USB4 devices at the expense of USB 3.1 compatibility? (Fingers crossed the M1 Ultra will be better, but I doubt it.)
It seems like there are some workarounds like connecting the USB 3.1 devices through a Thunderbolt 3 dock / daisy chain, which can sometimes boost speeds back to normal. Hopefully my existing OWC Thunderbay 4 TB3 RAID will perform decently.
Something to be aware of, for fastest external storage look at Thunderbolt 4, USB4, I think Thunderbolt 3 devices, also 10Gbe NAS, but probably not USB 3.1. Anyone with more knowledge on this subject I'd be happy to hear from! I will definitely do some testing and share my findings.... sometime in May after mine arrives.
PS I also decided to up the internal storage on my M1 Ultra Mac Studio order to 2TB for video editing. I’ve been getting by with 512GB on my MBP but it’s tight. My Mac Pro 5,1s have 1TB boot drives which has been fine, but I figured the 2TB internal SSD for the Studio would be more future proof and be a nice quality of life improvement.