Yes, with a wide gamut monitor that is calibrated, you should accurately see the colors in your raw images which are typically shot with ProPhoto RGB (ultra wide) or Adobe RGB (wide) color spaces. Not aware of any monitor that will do 100% ProPhoto RGB. There are several that can do 100% Adobe RGB. 5k iMac is P3. Note that both Adobe RGB and DCI-P3 are wide color spaces, but not an exact match. Adobe RGB has history in photography while P3 is from the video world.
http://www.astramael.com
https://creativepro.com/how-do-p3-displays-affect-your-workflow/
Depends on the quality of the original images (jpeg in sRGB vs raw in Prophoto or Adobe RGB).....and how much quality you want to achieve in the printed images. Most home printers are will only do sRGB.