+1 for EN521, but it’s a pinned AM/FR/Enduro rim now, not V-braked anymore, you’re thinking of the EX721 (wich used to be a 521, which was the V-braked DH rim). No strength difference between pinned and welded, welded just worked better with V-brakes and was marginaly more true arround the join as they’re ground flat afterwards.
Stiff rims are easier as they go out of true predictably rather than in huge uncontrolable wobbles while you tension them up. My first MTB wheels worked first time, my road ones too 4 attempts with a spoke tension meter!
Just go for something cheap off CRC, most of the strength is in the build anyway. I got some Funn XLraters for £16 each in a sale, they’re now back upto £40+.