For tile experts only please?

Bob, can I call you Bob?

Here's the deal, thin set is just that, it needs to be thin. No thicker than a quarter inch is recommended. You can get a medium bed mortar that you can go a bit thicker.

Not sure what you mean by cement mix since cement is an ingredient to concrete, sand mix and tile mortar. If the bag just says 'portland cement' it needs an aggregate mixed with it.

Back in the day we used to make our own sand and portland cement beds for tile. It was a six to one mix. They have cement boards nowadays.