First Time Build

Almost exactly my setup. Same Pi, LEDs, grabber and I too use a HDMI splitter though not that model. I only have 128 LEDs running from a similar 10A PSU, connected only at one end, without issue. Make sure you have a common ground. I used this guy's guide and tailored to my needs:

Hi

I am also following the above YouTube guide and have it running and working on my Windows PC using the Hyperion screen capture.

I have ordered all the parts (WS2812B LEDs, power supply, etc).

I am only going to be using with one source, my PS4 Pro so don't need a HDMI switch, yet. You linked a switch, not splitter btw. But don't think you'll need a splitter so the product in link seems correct if you have multiple HDMI sources.

The capture card on video is pretty much the same one you bought and it seems it's a common pick as nice and cheap and gets job done. I received mine today and wanted to test the loop back on it and sadly I am going to return it. Issue is, it only outputs at HDCP 1.4 as opposed to 2.2/2.3 which Netflix on PS4 Pro requires for 4K content.

So make sure this is something you are aware of as can't find any mention of it anywhere surprisingly.

I am now shopping for a compatible capture card.

I go with the general rule of thumb that each LED will require 0.06A of current at max brightness so 10A should be enough unless you are watching pure white screens a lot? ?

And yes, do make sure to have a common ground. Just run a cable from a ground pin on the Pi to ground on your new power supply.

Good luck. It's well worth the effort!

Edit:

This isn't mentioned much but it's sometimes recommended to add a 100 ohm resistor on the data line between the Pi and first LED. I think to prevent damage to data pin but I don't think it's necessary.