Macbook screen glitches when running external monitor

[EpicWizard]

Hi- bought my first external monitor for my macbook pro (2015), a Samsung U32J590. Suddenly I get my macbook screen glitching with various different patterns. Happens intermittently, and often goes away after a few seconds, but happens enough to make me concerned. Should I have gone with a smaller monitor? From the specs it seemed I should be able to run it- and apart from a little lag here and there it seems to run fine. Only running it at 30hz because I honestly can't find the 60hz option. Only using HDMI cables and tried both the one that came with it and another. Tried both HDMI ports.
The external monitor doesn't get the glitches.
Running 10.14.6.

If it's a matter of changing monitors- are there some things that make monitors more compatible with Macs? Because I'm having the issue of it not turning on after waking macbook from sleep and that seems to be a common issue all over the web with no solution as far as I could tell. :/

 

[Czo]

Connect it with DP (with a DP to HDMI active adapter) instead of HDMI. Intel GPU's from that era can not have enough bandwidth on thier native HDMI interface to drive a display like u have.

 

[EpicWizard]

Connect it with DP (with a DP to HDMI active adapter) instead of HDMI. Intel GPU's from that era can not have enough bandwidth on thier native HDMI interface to drive a display like u have.

Thanks! Ach shame. Shame because I think I made sure to pay extra for the graphics card upgrade- Intel Iris Pro 1536 MB, and the stats show it supports "up to 3840 by 2160 pixels on up to two external displays".

So- Borrowed a DP to HDMI adapter and it's so much snappier now (next to no lag), buuuut the quality takes a noticeable dip, and it's limiting me to 1080p scaling. At that point, having 32" is kind of pointless, although it's mainly the quality dip that's unfortunate. (unless it's a crappy DP adapter? Can't tell which DP version it is. It's AmazonBasics, they're usually fine.)

What would be the largest size monitor possible for me to run then via HDMI? 28"? Or what factors am I looking at to choose a replacement for the current 32".

 

[Czo]

Yes, it can, but only if everything is matching. Your Mac can output 4k@60Hz on DP connector, but only 4k@30Hz on HDMI connector. Both connectors had multiple versions in the past 10-15 years (if i remember correctly, you have DisplayPort 1.3 and HDMI 1.4 in your Mac), so you need a relatively newer DP to HDMI 2.0 adapter to achieve 4k@60 Hz. Maybe, your adapter is a DP to HDMI 1.0 adapter, because HDMI 1.0 caps out on 1080p@60Hz.

 

[EpicWizard]

Yes, it can, but only if everything is matching. Your Mac can output 4k@60Hz on DP connector, but only 4k@30Hz on HDMI connector. Both connectors had multiple versions in the past 10-15 years (if i remember correctly, you have DisplayPort 1.3 and HDMI 1.4 in your Mac), so you need a relatively newer DP to HDMI 2.0 adapter to achieve 4k@60 Hz. Maybe, your adapter is a DP to HDMI 1.0 adapter, because HDMI 1.0 caps out on 1080p@60Hz.

Ah- ok, dang, wonder if I can get a hold of a newer DP. I had to switch back to HDMI as the lower quality was actually giving me head/eye pain.

 

[EpicWizard]

So- I think I understand a lot more about the issue in the last hours. Looks like my HDMI connection supports 3840x2160 seemingly without issues, but anything between that and 1080 is putting stress on the graphics card with the scaling. Problem is that 3840x2160 is just too darn small for my eyes and I'm finding 3008x1692 to be the preferred resolution.
Edit: eh, glitches at every setting under HDMI. Just only partial screen when running 1080p or full 3840. Only other hope is then trying to find a DP adapter that gives a clear image.
Seems that all the DP adapters I'm seeing are 1.2, max 1080p. Still looking. But seems this is what I have to do as the HDMI port is underpowered.
Instead of an adapter to HDMI, can I just not get a miniDisplay to miniDisplay bypassing HDMI altogether since my monitor has that input?