Thanks for that information. Lots of useful details there, thanks for that 👍.
Yes lots of potential variation, which is why I think they are a more interesting subject than given credit for.
Strelets would have a bit of room for some "artistic licence" you could say. A chance to allow the designers and sculpters to express themselves while still maintaining a degree of historical accuracy.
As for the cap issue. Yes I agree having all and every single Hannoverian battalion wearing caps is likely not to be a historically accurate representation, but mixing some in with the other headwear on display is perfectly feasable. Strelets have mixed headwear in some of the other Napoleonic recent sets such as with the British. Some Shakos covered, some uncovered and some wearing the forage caps.
So any potential set could employ this philosophy if so wished.
Amongst other things the author accepts that the Feldjager may have worn green caps, but also suggests that while red caps may have been issued (effectively, as forage caps) to other units, their wear on parade and in battle may have been less-than-commonplace. A shako would be the regulation uniform when facing the enemy.
We will never know, and so artistic licence prevails. And I am quite happy with that...after all, nearly all my Napoleonic figures are much more uniform, and much less grubby, than they would really have been in the field.