Not with Dynomat you don't. You either get the one designed to do just sound attenuating, or you get the one designed to do both.
With Lizzard Skin liquid spray-on stuff, you do need both types. You spray on the acoustic dampening skin first, then do the thermal barrier coating on top of that.
Or you could use the acoustic everywhere, and the heat barrier only where you think you need it. Me I'd do it all if I was using Lizzard Skin.
As far as the others, with so many it's very possible that you need two layers of certain brands. But I've never seen that. Always seen one layer only, but of the correct type to help with both conditions.
Even with the traditional looking "jute" style stuff (such as from Quality Heat Shield) you buy the stuff with a single layer of foil backing for a little sound and a lot of heat rejection. If you want more sound blocking, you buy the one with the foil on both sides. You'd think that the shiny stuff on both sides would be more for heat, but according to them (this is 15 year old information) the double-sided foil version is for more sound deadening.
I'm assuming that adding an additional layer of just about any of the products will add both heat and sound barrier properties though. Just that I've never heard it recommended.
Do you remember which brand was talking about that?
Paul