You need to stop asking questions and get a bit more experience. It's all up to how you ride and what you're trying to do. If you're having trouble dealing with stronger winds then you need more practice.
The range of each size of kite with a foil is huge. You can ride almost any size you want and make it work. You've got vastly more bottom end than TT and surfboard, but you've still got the same top end.
You've still got the same body weight and you can edge a foil just as hard as any other kind of board. When you bear off the low friction of the foil immediately dumps excess power and you can swoosh around all you want.
I prefer my 4m in the high 20's up to 40+ knots. It's workable down to the upper mid-teens, but I prefer plenty of power so go for a bigger kite if it's lighter. The 5m is a nice all rounder and good for 15-30.
In the lower-mid teens almost anything works. I've been using my 12m in 10-20 because with lockdown sessions I don't want to be stuck underpowered. We're only allowed out for a limited time so I don't want to waste time changing kites. The fluttering of a depower 12m in 20 knots is a bit tedious.
With a tiny kite in huge winds I tend to avoid roll tacks. Getting them wrong in strong winds often results in an ugly spanking. Conversely, tacking a 12m kite in 17-18 knots is absurdly easy.
PS We have a few Cloud kite riders. They do twirly spinny tricks with big foils, zero buoyancy strapless boards and 2.8m kites