Impossible scrolling

The day I decided to switch from iphoto and tryed unbound I was very happy: beend able to organize folders the way I wanted was a good leap in been free. But folders have only one level, so all folders and subflders appear in the same place. And worts of all, every little scroll, while browsing photos, makes the mac stop and think.
I don’t have a new machine, but not so bad to justify this behaviour.
Can really imprrove performance

.ipa. about Unbound, v1.1.9