After looking at my tank earlier on I noticed one of my many MTS floating at the top of the tank. However, I am unsure as to whether it is dead or alive. The snail does not have the famous dead snail smell which I have experienced before with a dead Apple Snail and it isn't hanging out of it's shell but what I can see is the snails mouth but no trapdoor O_O

It is currently in one of those small medicine cups, still floating.

Should I wait a few days to see what will happen?

I've never had any MTS 'float', to me that would indicate putrification and gas build up in the shell, although as you say, there is no missing the whiff of a dead snail lol

I'd be tempted to keep him where he is in QT, perhaps lower the water level in the container and add a bit of cucumber. Plot any movement over next 12/24 hours.....