Well, for Space Engineers I actually run a server for the kiddos (and me from time to time).. If should appear in your game, it's set up though for cKs steam folk, so few people get on (none that we don't know).. We set it up as a public server, and there are just too many griefers out there, and too few server admin / utilities to prevent it (unlike minecraft, where there's a mod for everything, lol). You're welcome to join us any time... Anyone with MTX is here in my house, and pretty much the only people you'll see that I know of, lol..
I have played on a few servers out there, but my gripe with most is that they are too flaky - That's why I started one. I play on Sector Zero, and Promethius Rising, BEFORE it switched to a creative only, frequent resetting server. There was a really good one called Gerenom something or other, it was actually a split off of Promethius Rising when an admin and buncha people didn't like some of the rules there, but it has been taken down..
Many server have ridiculous rules and instead of fixing issues, they simply reset the server. I don't like that. If I spend four nights making a space station or ship, I expect to be able to keep using it - NOT have to start from scratch. That being said, Sector Zero is about the best out there now, that is a survival server with not too many crazy rules.. Don;t bother building on the planet though, as they reset the planet now like every couple days because they have a dumb rule about the map/world size.
Empyrion is on my to-get list, never seen the Interstellar Rift one, will have to look it up..
If ya do swing by our server, it's very much a work in progress.. Fly off wherever ya want and feel free to build up - Mine does have AI on (NPC ships) so beware!
There is a base by the starting area that I believe you are welcome to use to get started - But the ships, well certain ones like other servers, usually are enough to get ya going - Grind em up and remake what ya need/want