The only two that I would actually say are okay for almost everyone are weed and mushrooms. They tend to be safer than everything else and they don't cause any addiction. Things like stimulants and opioids can cause some bigger issues. Opioids are more addictive but stimulants are usually the worst for your health because they can cause heart problems.

How alike the high is depends on the drug. If two people have cocaine they will feel pretty much the same. With psychedelics their trips could be very different but they will still have some things in common. They may both see geometric patterns but they will "look" very different and make the two users feel very different.