Krita supports 16 bits per channel. Dunno about the rest.
I know how it works, since I used it for years. It is worth the money to buy Pantone-calibrated software and a Pantone-calibrated proofer. By calibrated, I mean the Pantone company has certified that those colors match their colors (although there are known limits).
When you say "Pantone XXX" in Photoshop, your proofer knows to put its calibrated Pantone color representation on the paper. Anything else is an RGB or CMYK guess, with nobody to turn to if things don't come out right. It's almost like buying a Red Hat service agreement and knowing you're covered rather than rolling your own and hoping you got it right, except in this case each mistake costs cold, hard cash.
You waste money with "Well, it looked right on the screen" and "It looked right on the proofer." One bad color caught after plates are made and the first are copies printed can easily buy a few copies of the entire Adobe Creative Suite.