Enjolras nods: he's fairly slim, for all that he's tall, so he and Duncan could manage well enough. (Well, he's tall by the standards of both their eras. By the standards of the 20th and 21st centuries, he's about average.) A bigger horse would be more comfortable for both rider and mount, though.

"This, or longer batons. But a walking stick is more practical." Because it's a standard fashion accessory for gentlemen of his day, and no one will look twice at a man carrying one around. Not to mention the fact that Bar will give them out. "I'll show thee something of it, if thou likest."