monitor for 2018 mac mini I just got a new, used Mac Mini as a replacement for my 2011 iMac. My plan was to connect my 2 27-inchers via mDP and use the iMac in Target Display mode using HDMI --&gt; Thunderbolt 2. Upon plugging it all in (and subsequent Googling), I think I learned the following:

The output needs to be Thunderbolt in order for Target Display mode to work, so trying to go from the HDMI port on the MacMini is no good.
Even connecting via TB, I still can't get audio or use the camera with the iMac in Target Display mode

Does that sound accurate?
With that said, I'm now looking into buying a 3rd 2550x1440 (minimum) 27-incher... one with speakers (which neither of my others have). I've been reading up on the latest mDP, HDMI and TB specs and quickly got in over my head. With a limited budget (around $300), I'm probably going to have to settle for less than the latest of each/any of these... most I've been seeing are HDMI 1.4 and DP 1.2.
I do web dev work... design and front-end development with some (very infrequent) video and/or 3D tinkering.
What advantages, if any, might I see if I were to bump my budget up and find something with newer HDMI and/or DisplayPort versions? What issues might I run into sticking with the lower versions?
I can say I have no complaints about my current 27-inchers (both with HDMI 1.4 and DP 1.2), but I feel like since I'm making a bit of an investment, it shouldn't be a dinosaur.
Target Display Mode has been deprecated for years. It has major limitations and many bugs and will only get worse with time because it’s unsupported. Don’t base your plans around it.