High notes eg F# E D and C# are too quiet compared to notes lower down the stave. Bars 184 through to bar 189.

I think that's just the reality of how a guitar sounds playing such a shortened string. Or at least, how the particular person who played the particular guitar played when they sampled it in creating the particular soundfont MuseScore uses. It's possible a different soundfont - or a different sound within the standard soundfont - might feature someone plucking the string that much harder to compensate. But you can also do this manually by selecting the notes you want louder and increasing the velocity setting in the Inspector.

It's conceivable an alternate soundfont - or an alternate sound inside the standard soundfont - might include somebody culling the string that a lot harder to redress.