When I was a very junior copilot on VC10s, the training captain, on a high altitude training detail, took the aircraft up to a little over 46,000ft to demonstrate the high and low speed buffets and he let me try it too. As I remember it, the high speed Mach buffet was of a slightly higher frequency and lower amplitude than the low speed buffet. There were only a couple of knots between the two, and gentle stick pressure either way induced one or the other. We didn't press it far into the buffet regimes so it was fairly mild. But one knew one was very near the edge of the envelope.
I cannot vouch for other types.