Changing DE, CLI or ISO

Looking to change from Budgie to Plasma and have a clean system. So which method would be better ?

To have a clean system, do an install from scratch with ISO

Concur with Alpha. Gparted. Nuke everything, Reformat it.
(thats how I approach all bare metal installs)

Always thought when I got to that point of switching I always started fresh.
Maybe tad more work but think it pays off.