A: Yes, New Game Plus is supported. However, I don't personally play NG+ and only do basic testing for it, so it's more likely to have minor bugs and balance problems.
A: Yes. However, an additional manual step is required because those mod managers don't install mod menus. Refer to the installation instructions for details on how to do this.
A: You didn't install the mod's menu file, or if using the next-gen version of the game, you may not have added the mod menu to the dx12filelist.txt file. Read the installation instructions again, especially if you installed using NMM.
A: It shouldn't really matter, but I would turn it off just to be safe.
A: Most likely you have your "user.settings" file set as read-only. The file is located in your "Documents/The Witcher 3" folder.
A: Check out the compatibility page. It lists many popular mods that are compatible and incompatible. If you don't find it there, you can ask in the comments section on the nexus. You can also just try merging them and seeing if the game launches.
A: Please read the description of the option on the ESGO Options page. It may answer your question. If not, try asking in the comments section and I may respond when I get time.
A: This is not a problem with the mod. You've probably hit the mod limit. Use one of the mod limit fix mods:
https://www.nexusmods.com/witcher3/mods/3643
https://www.nexusmods.com/witcher3/mods/3711
A: After working on the mod for about 3 years, I've decided that it's time to move on. I'm no longer going to change or add to the mod. I may still release small updates in the future to fix any bugs that are reported and to keep the mod working with future game updates.