Micro Sol is a decal softener, designed to make the decal more pliable, to conform and 'pull down' into the detail on the model surface.
Micro Set is a decal setting solution, designed to aid in the smooth setting of the decal, and its placement, when the decal is applied to the model's surface, having first applied the Sol to the decal when on the backing paper, after soaking in water.
Personally, I don't think there is much difference between the two, one being a variation of the other, and I tend to only use the 'Sol'.
However, if you have both, then use them, you won't be disappointed. BUT ! Follow the instructions to the letter, and don't be alarmed when the decals crinkle on the model's surface.
The Clear and Matt coat should probably be OK, but ensure you shake them well, and give them a really good stir before use. If in doubt, test some by brushing a little onto some scrap, and let it dry overnight.