Hi and welcome to the forum!
Am I able to import models and characters that I've made in DAZ Studio 4 or does GameStudio only support Maya?
Gamestudio does not support Maya directly, you have to export Maya models, f.i. as FBX, import and save them in Gamestudio's native model format MDL.
I don't know DAZ Studio 4 and its formats, but I assume it supports 3ds, obj or fbx for export and thus you can import your models in MED.
Will those models and characters be the same or will GameStudio decrease their graphic quality?
If there are no problems with import/ export, their won't be any loss in quality (EDIT: Your model
should not be high poly, that is below 10,000 triangles is ok.). It may be possible that your modeling program uses a specific material/ shader that you may have to recreate then.
And last question that I have is will the game be slow if the graphic is really good and if it has more than 1 GB?
This mostly depends on your knowledge and skill. The size of the game does not matter at all, you can make a game that's 1MB in size and runs at a maximum of 10fps or a game that's 20GB and runs perfectly fine.
