I have used Ostarine, RAD-140 and MK-677.
MK-677 I still do use quite regularly, excellent for recovery and sleep.
Ostarine gave me the best strength increases and helped heal a shoulder injury and there were very few negative side effects. Gained leaned muscle, became very lean, lost fat, maybe gained 2 kg's but quality.
RAD-140, gained 10 kg's, had extreme muscle pumps and increased aggression, my joints felt dry though so my strength was considerably less than Osterine, despite being a lot bigger.
I would use Osterine again though.