Someone more knowledgeable can chip in with some other models...

But so far I have found the smaller, cheaper drones just aren't FAST enough to keep up with windsurfing. For example the DJI Spark has a good tracking function which works nicely walking or running but it can't follow me on the board it just isn't up to speed. I was very impressed with the tracking software though on this cheap model, so I imagine the bigger DJI's (and newer ones) are even better.

Yea. Speed is an issue.

Don't rely on the follow function, you want someone in control with an eagle eye on the battery level, flying back against the wind chews lots more juice.
Find a mate with a Phantom 4, best option

Mavic 2 or Phantom 4.
Follow feature won't work for windsurf.

whenever i have my drone up everyone seems to think that you can set them up to follow people

All thanks to this misleading video (which was all a total scam) but had everyone excited.

they took $34 million dollars from 60, 00 customers and delivered nothing but wasted time and unrealistic expectations of how easy drones are to operate.

www.theverge.com/2017/1/12/14248988/lily-drone-tracking-dead-refunds

Stehsegler is spot on although it should be noted that the Phantom 4 gimbal is less able to withstand heavy maneuvering than the mavic 2s. Resulting in a camera wobble and pause on the p4 - usually just as a rider is doing their biggest move of their life.

I always seem to get some clown telling me that their $150 drone flies great and can do HD video - but its never the case.