Wonderful game. Orbits are very realistic, the only thing is the planets are all scaled down significantly for gameplay reasons, and the planets are not the real ones, some are replicas and others are just random. I'm playing on a trash computer but if you have a good CPU and GPU it should run fine.
So far here's what I have achieved in 5 months
Orbit (of course)
4 SSTO's, 3 work, the other has too much drag
1 Air Launcher carrying 2 Kerbals to LKO
1 Crewed rover to the Mun
1 Roving Base to Duna
idk how many satellites