I'm not sure if the most perceptible difference is between 75 and 85 or 85 to 95, but when I started my foiling journey, I was on a 90cm mast and things got substantially easier once I chopped the mast down to 75cm. It was not about foil control, but about the ability to reach waters deep enough to start. When you're walking upwind there's a stage where you lose traction on the bottom, and every wave or chop where you bob up and down will reduce or negate that resistance on the bottom, limiting or killing your progress. If you need chest deep to start, it will be significantly harder to reach that depth (through walking upwind) than to reach waist deep. If you don't have waves, or if it's not too onshore, this doesn't matter as much, but in my typical foiling conditions of onshore shallow profiled beach with waves, this made a hell of a difference. With skills and experience (a.k.a. eating shit over and over for years), you'll get to bodydrag better, waterstart faster and reliably, sneaking through gaps, so a longer mast will become usable again in terms of starting in onshore waves conditions.
So it's very dependent on your spot, and on your own size too of course. I'm about 1.85m, now using 82cm in every conditions, kite and wing, and I don't really see the need for anything longer. Longer masts do matter when you really want to angle the board very hard upwind, with high AR foil wings, typically for racing.
It's good to have only one size of mast, in terms of muscle memory and consistency in your foiling, so for that 75-85 is pretty good.