I have no experience with any of the Volla phones so not sure how smooth they are compared to the Fairphone 4 but of all my UT devices, it's definitely one of the smoothest and performant one. However, I'd say one of the main weaknesses of UT is the browser. It's outdated as we all know but in my observation, it also doesn't perform 7as well as you'd expect based on the system's overall performance. Not sure why though, honestly.
In any case, if you intend to use Waydroid extensively. Having more RAM is definitely a good thing to have.