25 years ago, (I was not yet in woodworking) we bought an IKEA kitchen. We have solid wood “frame and panel” doors. Nothing has moved.
The widest doors are 60 cm. Distance from groove bottom to groove bottom is 49 cm. Grooves are 1 cm deep.
Looking at the top edge of the frames, they are visibly made with shaper’s bits with complementary profiles.
I have an old garde-robe which also has panels about 49 cm wide.
So 49 cm wide panels are perfectly OK.
No limit (except aesthetic) for the height).
We have room doors with 56 cm wide panels, but then the groove are about 1.5 cm deep.