Best wide format Epson for refilling?

[Ink stained Fingers]

Light/photo inks are diluted inks which do not deliver much color saturation and don't contribute much to the overall gamut of a printer/paper/ink combination, you do not need diluted inks for saturated colors, light inks reduce the visibility of ink drops since they are lighter/less saturated. The number of inks do not tell you much about the overall acheivable gamut. If a printer comes with an additional color - like blue or red - these colors don't need to be mixed and give you a small gamut gain in this particular color range. This is important if you have to print colors colorimetrically correct - e.g. Pantone colors - you benefit from these additional colors, you may find some statement like that in printer ads that the printer model X meets 99% of a Pantone color set , and your printer without that red or blue only meets 96% of those colors even if the difference may not be much for normal prints. You are right that the number of colors does not impact the overall resolution, it is the min droplet size which is a rather important parameter, in combination with the driver and firmware since they control the droplet size, technical specs only specify the min droplet size, Epson printheads are typically driven such that they can emit ink droplets in 3 different sizes (variable droplet size) but you don't know at all which they are and which ones are actually used - all of them in a mix - or just different during different print passes and/or driven by your driver setting so printing is a pretty complex operation overall.