Zoro was more than likely sparing against and learning from the WGS/WSS Mihawk. Like he cant get any better training than that. Swords and their quality make a difference. Sure one can be an excellent swordsman, but theres a reason there are tiers/grades for swords. So yes it is indeed a power up, however its been shown that you need be very proficient in haki to control Enma. Seems he's more than capable enough.