A wetroom is usually part of a high-end refurbishment, so you can consider using a floating toilet. This will maximise the space (since the cistern is in the wall) and make it easier to mop underneath the toilet.
If the toilet is in the spray area of the shower, a floating toilet is better in terms of waterproofing. All toilets are waterproof, but if there’s enough water on the floor, this can make its way underneath the toilet and then down near the soil pipe. When you have a wall mounted toilet, the soil pipe is in the wall, so the water can’t get to the soil pipe, making it completely waterproof so you can have the toilet basically in the shower. This solves certain design issues when working with very small spaces.
