What are your priorities? A lot of pro photographers I know use iMacs because they are a cheap way to get an adequate computer attached to a monitor with high resolution and OK (for the price) color space
This is currently challenging because the 5K iMac is still on Intel which I’d be hesitant to buy into at this point. Hopefully resolved soon but we don’t know exactly when or what form it will take (e.g. will the 5K iMac be an “iMac Pro” and have a higher price than the Intel version?).
System agnostic (not an all-in-one), <35", HDR, OLED or OLED-backlight, >144hz, 1440p+ or higher, G-sync, 16:9, >=99% DCI-P3, doesn't look like a F-117 fucked a ferris wheel at an EDM festival, <$2k.