Sorry NapolOrk but I can’t comment on the suitability of those boxes since I don’t have any. However, Levi has already covered the key points pretty comprehensively.
The Austrians did use some of the men from the 3rd rank of Line infantry units as skirmishers on occasion though they weren’t as effective as the French. So at a pinch you could use some figures from the box if they are in a more dynamic pose. However, I think adding some Grenzers or Jägers would look nicer. One thing to remember is that troops cannot switch during a game from Line Infantry to become Skirmish Troops or vice versa. They are given their task before the game starts and will stick to that role.
Austrian Grenadiers were usually stripped from their parent battalions and concentrated in separate Grenadier composite battalions kept in the Reserve Corps. So historically they probably wouldn’t be mixed in with a line infantry Company but it’s your game. If you want to use Grenadiers I suggest you just create a narrative as to why they are present. I’d also recommend two groups of 8 if you do decide to use them.
The Austrians could be quite strict about uniform regulations I believe, except for senior officers. So most lower ranking officers such as found in an SP game would be uniformly dressed, but who really knows what events might occur in a campaign which might affect things.
I wouldn’t worry about the height of your gunners, it won’t affect the rules. Its simply what looks right to you.
John