Yeah, I use Ubuntu quite a bit myself. My mythtv DVR is a MythBuntu build. My fileserver is Ubuntu, etc.
Then you should be fine. A lot of people in this hobby have no Linux experience, but for you it should be easy.
Only worry is that the OS is quite a bit larger than the openelec OS's. That and I do not typically keep a keyboard/mouse hooked to these so anything done in Ubuntu would possibily involve dragging a keyboard/mouse over to it. I should just invest in one wireless K400 from logitech and call it a day...
16GB is plenty for Ubuntu and a small swap space. I don't think Kodiubuntu installs unity. It uses a lighter WM.
The keyboard/mouse thing is the hardest. Soon as those come into play (the Logitech included) the WAF goes out the window.
My advice is get a flirc. That little bad boy can take a remote signal and turn it into a keyboard press. Most of the interfaces for things like Netflix can be completely driven by keyboard, which means with flirc they can be driven by remote.
A flirc plus some good Harmony programing has hidden a lot of that stuff from my family. I personally don't do a ton of streaming stuff, but I do have emulators loaded in Kodi and the only sane way to control them (and exit them to get back to Kodi) is via a flirc.