I've got both boards and hoops , I use the hoops for smaller beaver but when needed will put a large or xl on a hoop if it's needed. But prefer boards for the larger size pelts.
As far as speed of the stretching of the pelts for me it's the hoops with a awl handy and a bunch of hog rings with a small block of wood to rest the hide on.

For me the smaller beaver I put up on wood every thing else on hoops I have bigger hoops 3/8 inch 4 foot round for biggest regular size for the rest down to about 50 inch it's easier for me on hoops but I only put up about 50 per year.

Lol , Plywood or OSB ?

Boards and nails.

I use 3/4 plywood. Most of my boards were from plywood taken off pallets. Usually under barrels that are shipped on pallets.

Same place I got most of my boards.

Yep that's where I've gotten all my boards. I work for a plumbing wholesaler and have asked my warehouse guys to let me know whenever we get good plywood in on pallets of ductile iron fittings or whatnot.