What is the best version of After Effects to use on my workstation?
First use the trial to test if it runs well on your system. It's the same version as the full version. If you start After Effects it will ask if you want to start the trial now (unless they changed the procedure since the last time I looked).
Adobe has this cloud apps overview tool that let's you install and update apps. Here you could also choose to install an older version and I think you can even install multiple versions side by side. However my recommendation is to work always with the latest version.