They can be used for all three dcat. I find that I don't much care for the high of tinctures but they will definitely get you high. The onset takes a long time, up to 45 minutes to an hour in some cases, and the high is quite dull for lack of a better word. It is difficult to explain unless you have tried it but the high is much more medicinal in effect. There isn't that happy, giddy feeling. More of a sluggish blah feeling. I definitely wouldn't recommend it for mood enhancement. It does work fair for pain relief and excellent for sleep.
As for your question about RSO, yes, it can be further reduced for exactly that. Mr Simpson recommends using a higher extraction solvent but the process is identical. I prefer alcohol because it is intended to be consumed, unlike many solvents that are suggested for RSO. The claim is that if done properly, RSO is safe using industrial solvents. I won't debate that fact except to say I prefer not to ingest anything that is used as an industrial cleaner. I don't mind loosing a little potency by using a less efficient solvent but that is up to each individual to determine for his/her own self. You extract everything in the same process with alcohol and then if you want RSO you will need to extract further. I use a double boiler method and cook the tincture down to oil. A glass or stainless bowl setting in boiling water and watch the temp of the tincture or you will ruin it. The tincture will cook down to a very dark consistency but will still be liquefied so long as it is warm. As the tincture begins to cool down it will thicken to an oil, or is allowed to go too long, a blob of grease which is basically THC with some chlorophyll and residuals. It takes a little practice to get proper oil.
Hope that helps my friend.