Because the Kailh Speed switches are the same size and general shape as Cherry MX, there should be no problem with keycaps on them. You'd just don't press them down as much.
You would only see compatibility problems with some keycaps for Cherry MX on smaller switches, such as low-profile switches. (such as Tesoro Agile, Cherry MX Low Profile, Kailh Choc V2). On those, however, the keycap could reach the bottom before the switch does.