XComp by Gugen Studio aim to facilitate the comparing interaction between renders and render region by performing a fast compositing.
It is a stand alone software released under MIT license, it works on Windows Linux and Mac OS.
Gugen Studio:
https://gugenstudio.co.jp/
XComp download:
https://github.com/gugenstudio/xComp/releases/tag/v1.1.7
auto-save render download:
https://github.com/jeinselenVF/VF-BlenderAutoSaveRender/releases/tag/v1.9.2