High Sierra post install issues help

I've recently built my first Hackintosh. After getting through the install with less trouble than I expected there are a few things left I'm trying to sort out. My Google-Fu is failing me.

This first issue is in trying to get more than 1080p out of the onboard HDMI. I did the install while connected to a 4k T.V. and now I have it connected to my ASUS MG279 1440 display vi HDMI. In both cases I can only get 1080p. In display preferences if I select scaled It give me the options "1600 x 900", "1080p", and "720p". I thought I might have a really old HDMI cable so I purchased a new one; but nothing changed. Googling seems to indicate that there should be nothing to do. It seems like it's just expected to work at higher resolutions.

My second issue is with audio. In Preferences -> Sound -> Output I have the following devices "Internal speakers (Built-In)", "Line Out (Audio line-out port)", "Line Out (Audio line-out port)", "Digital Out (Optical digital-out port)", and "Pioneer VSX-LX301 DDDF3E (AirPlay)"

I'm not sure why I have Line Out listed twice. Could it be the output on the motherboard is one and the headphone jack on the case is the other? Plugging the minijack cable in and removing it and plugging it in again seems to "randomly" connect it to either of the Line Outs or the Internal Speakers and I have to go to preferences and select a new device until I find the one that actually makes noise.

Speaking of noise, when I have the audio cable connected I get a constant hum with the occasional squeal out of my speakers. My audio set up is complex. I'm sharing my PC speakers between a P.C., and Amazon Echo Dot and the new Hackintosh by passing all the audio through a Yamaha mixer. With just the PC and Echo connected all is quiet until one of the devices intentionally puts out a signal. As soon as I connect the Hackintosh I get noise. I even get the nose if I turn the Hackintosh's output all the way down on the mixer. As soon as I disconnect the cable the noise stops. Could a "driver" or kext fix this issue? I'm going to order a ferrite balun to see if that helps. If I can't get the noise out of the line I'd settle for getting the audio through the monitor's built-in speaker; but HDMI isn't an option in the Sounds preference pane. Googling how to get HDMI audio working seems to only present forum posts or guides that expect me to know more about hackintoshes than I do and don't provide links for the background info that I'm lacking.

Any help or insights would be much appreciated!

My Hardware consists of the following: MLB: Gigabyte GA-H270N-WiFi Proc: Intel Core i5-7500 Graphics: Intel HD 630 RAM: 16GB Ballistix DDR4-2400 (2x8GB) Storage: Samsung 500GB EVO SSD Chassis: IN WIN Chopin WiFi/Bluetooth is still what came with the mother board. I have a broadcom board on the way. That'll be a whole other issue!

I followed this guide to get High Sierra installed: https://logicbugs.com/mac-os-high-sierra-hackintosh-guide/

I went with High Sierra because I couldn't down load Sierra from the App store any more.

Thank you in advance.