Is the Vitodens 200-W sufficient for underfloor heating?

It is not a heat pump. You can also work sensibly here with individual room control...
Depending on the size of the house, the supply air temperature must also be higher.
The problem here is probably the flow rate.

Rarely have I read such nonsense. Except for the issue with the flow rate.

The gas heating can still run efficiently. It is not a heat pump. The energy required to raise the temperature by, for example, 10 degrees is almost always the same. With a heat pump, it makes a difference whether it's from 20 to 30 degrees or from 50 to 60 degrees. And with large houses, higher flow temperatures are needed because of the distances. But presumably, our idea of large is different..

I think jojo just doesn't know your house ;)

And for large houses, higher flow temperatures are required due to the distances. But presumably, our idea of large differs..

Our house is also 125m2 and it does not need to be blasted with 47 degrees at 0 degrees outside temperature.

However, the Te does not mention any details about the house. Detached, townhouse, year of construction, insulation, etc.

Our house also has 125m2 and it doesn't have to be blasted at 47 degrees with 0 degree outside temperature. The OP, however, does not mention any details about the house. Detached, terraced house, year of construction, insulation, etc.

As far as I remember, Rick's house is slightly more than 125m². :D

I am completely with here; the flow rate is obviously too low, but probably not due to incorrect settings on the HKV (although this can of course make it more difficult), but rather due to insufficient power of the Vitodens's installed pump. It simply cannot "push through" all the circuits properly, so the rooms remain lukewarm because the energy just doesn't get through.