Ask far as I know (I'm a user not a dev), it shouldn't make a difference as all come via RD, so the speed or buffering will be dependent on your internet connection and connection to RD servers.

I personally turn off hosters and scarpe only one torrent site (torrentio) as it's super fast and gets enough links). But I use fen primarily, with Seren as a back up.

I have fairly slow internet and never have any buffering issues. I would suggest looking into your video cache setting (Google Kodi advanced XML settings link to Kodi guide) or set Seren to select only smaller file sizes.