I think the through the mouth smelling in called Phleming (spelling?). It sounds terrible, but cats do have an extra scent organ in the roof of their mouth. Males do this a lot when they're trying to track down a female in heat.
I've only ever had one cat that panted and that too was only in car rides (usually on the way to the vet's). Tabis would just sit in my lap and pant and drool all over me.