On the formula side of the question - yes, someone at 75 kg can hold down a formula sail in 20+ knots. I weigh 79kg and have had the Starboards F175, F147 and the F160. The 160 is still going great so I will keep it another year, or longer.
My skill level is no where near the top amatures or pros, so I go a bid conservative with my sail selection when racing or sailing formula. Top formula sailors will pretty much limit their sail quiver to something like 12.0, 10.5, 9.2, expecting to use the 9 meter sail up to 25-30 knots.
For me, I have an 11.0, 9.2, 8.4, but I have gone down to 7.6 and even a 6.5 with winds up to 30 knots, but that is just for racing. For fun, I would never go out with anything smaller than the 8.4. In that wind, I will be on my iS 111.
Formula is designed for upwind and downwind so that's where the challenge is and where TOW plays a big role. It's also where the fun and excitement is.