Extremely individual...
I have found masts below 90 cm to be useless for any fun, both flat water and waves.
Some like these supershort masts.
I prefer my 92 cm mast.
100 cm is fine for super choppy wave "mess" indeed, but often not needed.
I would aim for 90-95 cm if going for a mast for fun in waves.
Racers use longer masts, 110-115 cm, but makes no sense for freeride fun.
Shorter masts are great in marginal winds where difficult to get out to deep water, but thats it, apart from that only disadvantages IMO.
Peter