Fidelity in the print is related only to the pixel resolution being delivered to print. 300 ppi is at the high end - I once heard that magazines print at 150 dpi - and will produce sharp images. Anything larger is wasted.

If you desire a 3"x5" print, you deliver a 900x1500 pixel image. That said, I have gotten many fine 12x18 prints from a 6mp image (3000x2000).

But if you're looking for a 24x36 print which yields no flaws when viewed from four inches, you're looking at 7200x10800, or a 78 megapixel master. I hit this number occasionally with multiframe stitched panos from my 12.6 mp camera. Processing a file that size is awkward with 8bit JPG and scales in difficulty with lossless formats.

The format of the image master makes no difference. If, though, you're extremely particular, a no-loss format like TIFF is marginally preferable to a lossy format like JPG, even with highest JPG quality selected. Due to processor and storage constraints, I rarely use TIFF.

Color fidelity is managed by taking into account your monitor profile and the profiles and technologies of the printer you're sending to.

But none of this addresses sharpness. Sharpness in the print is delivered solely by your lens and a steady hand.