The oil finishes... First of all, the labels on finishes are not necessarily honest. There is no standardization of terminology and the industry is thick with meaningless trade names.
100% tung oil is oil from a nut. It does harden over time when exposed to oxygen, but it needs to go on very thin and every coat must dry for days. It does create a cured layer, but I don't believe it is particularly hard nor durable.
Danish oil is an oil / varnish blend. That means it has some of the air curing oil in it (Linseed?) and also contains varnish solids, and varies by manufacturer. These solids deposit on the surface of your wood as the solvents evaporate. A varnish finish tends to be tougher and more durable.
Tru Oil is a trademarked name of a specific varnish hybrid, but depending who you ask, may have other secret things in it. I know several people who use it on necks and love it. I used it on a neck and for a whole uke last year. I was concerned about the oil soaking into the top too much and doing something. I don't know what, but ignorance is not always
. Sometimes it's just paranoid. Anyway I did a couple of wash coats of shellac over the whole thing first. Turned out great. Again, very thin coats, and lots of them with plenty of drying time between. I think some folks will do 2 coats a day, especially if it's warm, but I waited at least a whole day between coats. Too thick or too soon and it will not cure well.And all of these types of finishes are the ones that can spontaneously combust so don't leave the rags lying around even for a few minutes. Don't burn your shop down. It is a very real concern. I hang mine to dry outside so they get plenty of airflow and don't build up heat. Once they're dry, they are safe.
Mike