I recently installed ubuntu 18.04. I also added the PPA
ppa:oibaf/graphics-drivers to have the latest version of the driver.

Now, when I try

DRI_PRIME=1 glxgears

it usually works fine, but sometimes the system freezes when I maximize the
window.

The other software I mentioned, i.e. "Visual Molecular Dynamics", crashes much
more frequently, maybe because its 3D job is heavier.