wrt the original question, I would look at both sail and foil change for higher winds. For a 5 knots increase though, I'd go a smaller sail size to make handling more comfortable on whatever foil I was on.
I have an NP Glide and picked up the Small and Medium size Wings 2nd hand to go with the Large I have learnt on. I like the Small in 4.2m conditions (like the video below), the Medium on 4.7-5.7m wavesails and now only use the Large with a 6.8m Foil Sail for lighter conditions.
On the day of the video, forecast was for 15 knots, but turned out to be 20+ (screenshot) and I didn't take my smallest 4.2m sail

, so hung onto the 4.7m, Small Wing

Turned out to be fun, but a little hectic.