They should be a lot tougher.
These were infantry units that had in previous wars distinguished themselves. As a reward the entire unit was designated a Guards unit.
The other type of Guards are the infantry units whose job it is to guard the monarch. Typically there would be enough of them to form a unit of their own. Life Guards is sometimes used to distinguish between the two. They guard the monarchs life
These units, especially the latter were the most elite in the army. These were the absolute best soldiers they had and it was the most honorable post to hold. Even being a ground infantryman.