Styrofoam granulate at different raw building floor heights

Hello, we are currently planning the floor in a single-family house to be renovated on the ground floor. The house is only half basemented, and the shell structure in the basemented rooms is higher than in the non-basemented rooms. If we now add styrofoam granulate (then underfloor heating and screed), there will be 12cm of granulate in the basemented rooms and 28cm of granulate in the non-basemented rooms. Can someone tell me if this could cause a problem because the granulate will settle differently over the years? Would it be an alternative to bring the non-basemented rooms with styrofoam granulate to the same level as the other rooms and then lay insulation boards everywhere? Thank you very much! :)

Why granulate and not just regular floor insulation (boards)? Everywhere, only in different thicknesses.

A screeding company would do everything only with granulate, the other company would do partly granulate and then panels on top. Honestly, it hadn't occurred to us to do panels everywhere, but we don't know what speaks against it. It is only important to us that the floor does not settle unevenly due to the different raw construction heights.

Depends on the level of unevenness. Insulation boards only work if the floor has been leveled, which is rather unlikely. I would take the approach of the 2nd company: fill layer for leveling, then insulation boards for the corresponding height.

The floor is leveled, so it has no unevenness, but it is not necessarily 100% horizontal everywhere. Therefore, we thought that granulate is rather better, also so that the underfloor heating rests on an absolutely flat surface.

Then you can also work with floor insulation boards. In [Waage] it is installed through the screed