Install ubuntu alongside kubuntu?

Hello, I have installed kubuntu 16.04 on a laptop. It si sowkring ok, but it is quite slow and lagging, probably because of the ATI graphic card (proprietary drivers are no longer available, it seems...).
I was thinking to try ubuntu, and wondering what is the cleanest way to install it and, eventually, remove it and go back to kubuntu.
I have made a lot of configurations on the kubuntu desktop, so I would like to keep them.
Thanks!