If you're planning on using an AMD graphics card with Ubuntu 18.04, you have a couple of options. Because Bionic is an LTS release, you do have the option of using the proprietary AMDGPU-PRO drivers. The open source drivers that come with Ubuntu are probably better for gamers, though. They're already installed, and you can configure your system to receive constant performance-boosting upgrades from the latest Mesa releases. Either way, you're going to have great experience working with AMD on Ubuntu 18.04.