My 4K instance has one root path (different from non-4K) and one quality profile that's auto-selected by default. Using the Radarr connect option, I have a quality profile on the non-4K instance that automatically adds the movie to the 4K instance. This way, you can ensure you have both 4K and non-4K copies of certain movies (e.g., for external access/transcoding). You also ~never need to actually interact with the 4K instance. See this page for details: https://trash-guides.info/Radarr/Tips/Sync-2-radarr-sonarr/
For Sonarr, it's also for separation, but less of an issue if you're on Sonarr v4. The one thing you gain even on v4 is the ability to have different quality definitions for anime and non-anime content. See: https://trash-guides.info/Sonarr/Sonarr-Quality-Settings-Fil...
For anime first time I've heard that suggestion but anime in general is super annoying to download due to not having real seasons or whatever often. Wonder how it helps..
If you're not using Plex or find it doesn't work so well for Chinese subs, can also try bazarr which does the same thing with subs but is a standalone software.
So with the above setup you can download the actual series from wherever and then it'll fetch Chinese subs for you and add them automatically. Otherwise for actual Chinese trackers try share.dmhy.org and mikanani.me for public trackers.
Feel free to shoot me an email(in my profile) if you need any advice or help setting anything up :)
You either have to commit those preferences to a tag that you try to remember to put on everything (fiddly), or you just commit to them being on everything you download regardless of whether or not it is anime, which can cause weird selections when sonarr is sourcing western media.