QuickPic used to be a powerful and lightweight gallery replacement, with more than 10 million users. I used it a while ago, but when I wanted to reinstall it today (11/02/2019), I couldn't find it in the Google Play store. I don't believe this is because of device incompatibility - I tried this on 3-4 devices, most of which it has been installed on, and I didn't see it on the desktop site either. The last version I found online is 4.7.4, uploaded to uptodown in Sept 2018 (link).
This XDA news reports that the developer, Cheetah Mobile, was involved in a case of ad fraud recently which resulted two of it's apps being removed from Google Play, neither of which is QuicPic. This blog post however reports that shortly after the case, Quick Pic indeed disappeared from the store.
The main features I liked it for were, if I remember correctly (it's been a while since the last time I used it) :
My questions are: