I've been there twice, last time in Nov. 2021. If you like freeriding and bump&jump, Kanaha Beach Park is the place to go. Great wind in summer every day from 11am on, nice beach, water as flat as it can be in Hawaii (2ft chop, further outside in summer around 1-2m swell).
see my video here:
best for rental place there is clearly Kanaha Kai. They have great Starboard boards, HotsailsMaui sails (HSM factory is just next door). Around 60$ per day for a board and two sails.
as for location to stay. of course if you only go windsurfing, stay at the north shore. lower Paia is nice, and also very close to Hookipa (world famous, experienced wave riders spot).
if you like beautiful beaches, nice restaurants etc, the south shore is better. I loved Lahaina for its beach-front restaurants and stores, but that is a 45min drive from the mentioned windsurf spots.
Kihei and Wailea are also nice to stay, but no beach-front restaurants and so.
And yes, Maui is really expensive. But worth it!best regards
mariachi76