i have the newest iMac on the market. All usb-c/thunderbolt 3 ports and usb 3.0 ports. No thunderbolt 2 ports.

I just got off with Apple Support and they confirmed the newest iMac only supports HDMI connection to second/3rd party monitors. It does NOT support DisplayPort anymore.

I have a brand new BenQ 2700 PT. However, I also got off the phone with their tech support and they absolutely confirmed that the HDMI cable/port, while it 'works' with Macs, is NOT optimized for proper display of colors and signal (again, Macs only). I know this, because the reason I called them to begin with was I was connected from the BenQ to the iMac via HDMI and the colors and sharpness were WAY funky.

So my question: what brands/models does anyone use, that are connected to a Mac via HDMI, and you have no problems, off-colors, softness, etc etc.

Looking for any/all recommendations. My budget is at or under $1200.

If your work is color critical: buy the best EIZO CG which you can afford and you will never regret it.

Second on what anchev said.  A well know colorist in LA ditched his Thunderbolts for the Eizos.  He said the shadow detail was awful in the Apple screens so he was in Samy's buying four large screen 4K Eizos to replace them.  His own feeling was Apple left the pro market for the saturated colors and contrast of the amateur market.

That doesn't sound right. Don't the Thunderbolt 3 / USB-3 ports support DisplayPort? I use a USB-3 to DisplayPort cable to connect my MacBook Pro w Retina Display (Late 2016) to a 30" 4K DisplayPort monitor at 60Hz.

In fact, according to the iMac specs on Apple's site, the Thunderbolt 3 ports absolutely support DisplayPort. Check here: https://www.apple.com/imac/specs/. Scroll to the section titled "Video Support and Camera," where you'll find the following:
"Thunderbolt 3 digital video output
Native DisplayPort output over USB‑C"

Scroll a little further for the pic of the back of the iMac, which has the following text labeling the Thunderbolt 3 ports:
"Two Thunderbolt 3 (USB-C) ports with support for:
DisplayPort
Thunderbolt (up to 40 Gbps)
USB 3.1 Gen 2 (up to 10 Gbps)
Thunderbolt 2, HDMI, DVI, and VGA supported using adapters (sold separately)"

Either I'm misunderstanding what you're trying to say, or someone you talked to at Apple Support was misinformed. Or the Apple site is just plain wrong... which seems pretty unlikely seeing as Apple's usually pretty good about that stuff.

It occurs to me that what Apple might have been saying is that you can't use their Thunderbolt 3 to Thunderbolt 2 adapter for a DisplayPort monitor. (The adapter just doesn't support Thunderbolt's display capabilities.) And Apple doesn't sell a Thunderbolt 3 to DisplayPort adapter, but they do sell a Thunderbolt 3 to HDMI adapter. So in that sense, Apple themselves cannot offer you a solution for connecting a DisplayPort monitor to a new Thunderbolt 3-equipped Mac.

But...

Because the Thunderbolt 3 ports do indeed support DisplayPort, you can absolutely use an adapter to connect to a DisplayPort monitor natively. That means full support for all color management, resolutions, monitor profiles, etc. Here's one I can vouch for as being rock solid through eight months of daily use: http://amzn.to/2vPX5SI

It works great with the Thunderbolt 3 ports on my MacBook Pro, and the manufacturer explicitly says that it works with the new iMacs.

You have to buy the correct cable that utilises the Eizo's features. Apologies for I do not know the specific one but if you scour Amazon etc and read reviews there's a lot of discussion on it. The trouble with Apple is they don't really care about anything non Apple endorsed, so while there are always valid options you just have to discover them yourself.

Yeah if you can through a stack (slang for a thousand dollars) on a monitor then get either an Ezio or a Nec monitor. That's like the end route when it comes to color accurate monitors. spec wise both are really nuanced in their changes, so it's up to you and what you do exactly, but yeah chose from one of those two brands at that point because nothing else really compares to the quality of those high-end monitors.

There is also the Dell "u" series. I have been using them for a while. Well, the 30" ones at least. They the cheaper option (still a £ grand + each), still IPS panel and calibrate to 100% Adobe RGB (the 30" ones are wide gamut monitors). I have went through Dell u3011 (now dead) and now use Dell u3014. Colours are pretty accurate after calibration, but panel uniformity is not the best.

As for Eizo or Nec, I have been using 30" monitors for good few years now and I just couldn't go back to a smaller screen. 30"+ Eizo / Nec monitors are crazy expensive here in UK. You are talking about £2k+ for one.