Hi.

I'm planning to install this great mod, but I have question regarding old save files.

Well, my brother is doing casual playthrough, his first time in the game, and I don't want to mess up his save file... again. If I install this mod, and not touch my brother's save file, not load it or nothing, and uninstall it, will it be in the same state it was before?

Also, can someone please tell me what there are other immersive or quest-adding mods that are compatible to JSawyer?

If you never load a save with a mod active, then it won't affect the save if you delete the mod then load that save. So, no it won't mess things up.

However, you might want to look at the Mod Organizer as that allows you to have different mod mixes for different characters or saves or whatever

http://wiki.step-project.com/Guide:Mod_Organizer

Another thing I would do is make a backup of his game saves and put it on usb flash drive just in case.