what is the best way to remove decals that are not under a clearcoat

peel em off, start slowly, You might benefit from the heat of a hair dryer or Set it in the Sun for a while,
If you find it leaves any sticky residue, try a weak solvent, Sometimes WD-40 will even remove residue,
Mineral Spirits is also Mild, many choices

Dave

A combination of 3M adhesive remover and plastic razor blades is what I used in detailing cars. Some of the other guys preferred using a heat gun instead of the 3M solvent.

As above, mild heat application will be helpful. Start at a corner and peel slowly. Residue can sometimes be removed by rubbing a piece of clear packing tape onto it and using the tape to peel it off. Sometimes you can "roll" the residue off with your thumb. Otherwise citrus cleaners will often turn the residue to a gummy "snot" which can be rubbed off. There is a line of products called "Goo-Gone" which may also help. https://www.googone.com/ I've never used the 3M adhesive remover but have heard of it being highly spoken of. Mineral spirits and alcohol are also sometimes effective.

Lighter fluid also works very well to remove the residue.

It's easier, the shorter the time for removal, after they were applied.. ..

I've never tried it but hear that Goof Off works good.

I did it this weekend. I used a flexible plastic card about the size of a credit card. Started it and peeled it off. It took off the upper layer and left the under layer. I used mineral spirits on a towel and wiped it over the residue. Waited about 2 minutes and took the plastic card back to it. Took it all off. No fuss no muss. Plus you get shiny new rims.

goof off or acetone