I‘ve a lot of Problems with the combination AP and Wacom Intuos Pro on my mac too. And I‘ really pissed on this situation specially when I see that PS elements works perfect with the Wacom tool.
Nothing works really good using the graphic tablet for AP. Some problems are described above (e.g. brush size and hardness). But also more simple functions didn‘t work. To use the wheel for zoom or/and scrolling isn‘t possible. I can configure ist in the Wacom settings but it doesn‘t work in AP.
If AP is truly to be seen as a (Adobe) replacement, surely this has to be overworked extremly. Or ist AP only a unambitious solution for amateurs only using mouse?