Preferences/Settings were the first place when I looked, but … I’m at the front of my system and:
-composition window – preview quality: high
-composition window – preview resolution: full
– render in draft mode – unchecked
Transition quality is poor … soft images, looks like in draft mode – sorry.
I try preset: Library >Transitions/DVE Transitions/Wipes/QuadBar DVE
It is interesting, that not all presets are poor ! Some looks perfect.
I use only presets for my tests.