Because I know some groups get their raws of Chinese sites and so on, but don't most of them have watermarks on them? So do groups just edit these out without consent or

No. It's true that there are watermarks occassionally, and some groups edit them out, but...
I'm pretty sure some groups do ask for permission from the Chinese group - Red Lotus, and nyx studio are some Chinese groups.

Usually, only manga scanlated by a Chinese group contains watermarks.
Sometimes, there are manga published in Chinese and directly scanned. There are usually no watermarks, or very basic watermarks, which are very easy to clean out.

Most scanlation groups use manga published in Chinese that were directly scanned to avoid watermarks. Or if they want HQ raws with bad watermarks, they'll use the scanlations instead (and clean out the watermarks).

Another possibility is they use the Chinese raw to translate from, but use the Japanese (or other language raw) because it is a higher quality.

I'm not sure, but this is my guess.

Semi-retired.

I find that many scanlators buy their own copies but I believe they ask permission if they are getting the raws from a provider. If they don't, then I have to say that they are complete hypocrites considering most scanlators ask that others ask them for permission.

If anybody bothered to read the credits page in scanlation releases, they'd see that they do often credit the raw provider. It's not a universal thing, but that's where they are.

Sarcasm just doesn't work over the internet.