Hi Nesjett,
Yes, open the AndroidCamera.h and change the resolution by change the value on width and height, but remember higher values eat performance.
if you want set your camera texture as background you need calculate the distance of the plane based on FOV, of course the plane size must match with the texture resolution, quick formula: float distanceToCamera = (texture->GetSizeX() / 2.f) / FMath::Tan(PI / 180.f * (horizontalFOV / 2.f));
as far as I know you can access everything in blueprint if you want, even your FOV.
Hope helps
Cheers!