Youtube channels do have RSS feeds, so if you want, you can subscribe to all the rss feeds for all the channels you follow.

I don't think there's an rss feed for "a selection of new things that youtube expects that you would actually watch, from the channels you follow, which youtube would list on the main page or whatever for you", so you can get exactly the same things,

but if you just want to subscribe-through-rss to all the channels you subscribe-through-youtube , you can.

You can also subscribe to a youtube playlist, if a channel has a playlist you are interested in, but which is only a minority of their videos.