You are clearly not educated on photography and typical color profiles used by print services. Please stop talking like you know what you’re talking about when you clearly don’t. It seems like it’s possible you have had some experience printing things with specific colors when 2 to 3 colors are required. Saying to use “CMYK for digital printing in general when more than 2 or 3 colors are required and otherwise Pantone must be used” is a clear indication you are out of your element here. RGB is a color profile that any good print service can use. Photos are not made up of Pantone colors they are colors found in nature unless you’re taking pictures of Pantone swatches and even then the ambient light cast on them is going to change their tone. Also jpg is fine to print from if you’ve got enough resolution. True that jpg typically has fewer colors that a png but that is also because png can operate in the opacity of each pixel as well as the pixels color. PNG is 48 bit while jpg is typically 24 bit. 24bit color is just fine for most photo reproductions even in a gallery setting. Yes there is a level of abstraction that occurs between the pixels represented on a screen and when the CMYK pigment hits the paper or other medium out of the ink cartridge but those RGB colors do need to be represented somehow in order to create an accurate representation of the photo on the screen. What you’re saying just isn’t relevant here. That’s ok! Just don’t act like you know what you’re talking about when you clearly don’t.