I was shopping for longer HDMI cables on Amazon which prompted me to read articles about what I really needed. Basically there are a ton of different terms used in the description of HDMI cables. The amazon basics HDMI cables support 4K at 60 hertz. The only time you would need to consider and upgraded premium cable is if you were attempting 8K. In my setup I have two monitors connected to display ports on my gaming PC using. I use a third HDMI port on my 1080ti that runs to my Elgato 4K capture card on my streaming PC. I have no issues whatsoever with the HDMI signal at 4 k. And your configuration where you're wanting to separate inputs you would need to control the signal. You could go through the hassle of swapping the cable from the gaming PC with the one from the PS4 when you wanted to capture that video/audio. I would suggest a simple HDMI a b switch so that you can leave the cables connected and just choose what you want being fed to the capture card. You would then go HDMI out of the Elgato to your gaming PC. The 4K 60 will pass through 1080p at 240 hertz or 1440 at 144 Hertz with no issues. From what I've read from testers you do not see the delay. In a dual PC set-up you need to clone your gaming monitor to output via HDMI to the Elgato card. So if you use a switch to route your PS4 and your gaming PC's outputs the only thing you would have to do is swap inputs on the gaming monitor depending on what you would want to see. Sorry for all the bad grammar but I am just dictating this and hoping Google does it mess it up too bad. I'm putting the links below for the Amazon cables that I can say do work. Also is an HDMI switch. I had to edit this because I accidentally hit the button. When you do your shopping don't get too caught up in the labels or descriptions. A 2.0 HDMI cable will work just fine with a 1.4. make sure when you're looking at switchers that you choose one that supports 1440 at 60 hertz. And these are not affiliate links below just did a quick search and copied and pasted. Good luck
Cable https://www.amazon.com/gp/aw/d/B07RZ1JHMM/ref=ya_aw_od_pi?ie=UTF8&psc=1