In the Napoleonic Wars the regiments of Dragoon Guards are certainly heavy cavalry. The Dragoon Guard regiments had been Regiments of Horse, but were slightly downgraded (they could have slightly cheaper horses etc) to Dragoons. They were given the title Dragoon Guards to differentiate them from existing Dragoons, who they considered themselves senior to (and better than!).

Dragoons at the time had lost their dismounted role, which is why we had to have Light Dragoons. Even then, the Light Dragoons would never dismount. so we ended up having mounted riflemen in the Boer War by giving horses to infantry. You can never get a cavalryman off his horse! (see also HuwG post of 25 May).

It would be most expedient to send more than one person to check on enemy movements. If you only send one, you might not get him back! Unless he's a spy, in disguise. If you were sending an aide, because you needed someone whose ability you trusted, you would at least tell him to pick up an escort from the nearest light cavalry.