Ceramic tile is to some intents ceramic tile … obviously quality differs and there are 5 grades (from memory) where 1 is light domestic and 5 is heavy industrial – prices are not unreasonable for the industrial .. I used grade 4 on my kitchen and its incredibly strong … takes forever for the underfloor heating and when it does the heat is very localised (you can see where the coils are if its wet) … so it’s insulating well
I’d imagine the lower the micro-porosity the better the thermal insulation but we are talking about a material used as heat shields on the space shuttle …
Instead of using plasterboard for the partition you can also use cement board (cuts with a knife) or the silica stuff.(nasty to cut – best done outdoors with a mask).. which is rated fireproof and you can use to line fireplaces. Tiles stick to it no problem, I used the thin cement board in a bathroom to tile on top of as I didn’t want to raise the floor… but they do 9mm and 22mm from memory
Both are also waterproof which is always good in a kitchen.