UGREEN Headphone Splitter for Computer 3.5mm Female to 2 Dual 3.5mm Male Braided Audio Splitter Cable Microphone Stereo Jack Earphones Port Cord Gaming Headset to PC Laptop Adapter Black

You'd want a headset splitter, something like this.

The 1/4" output is balanced, so I'm curious what you're plugging that into. Is the cable a TRS cable, or a TS cable (if it's TS, then you're shorting the balanced output). As far as the headphone output goes, I'm a bit confused. You've mentioned plugging in USB headphones? That can't connect to a 3.5 mm headphone output. If you were using a 3.5 mm headset, my first guess would be that the headphone output on your amp does not like having a TRRS headset plug plugged into it, so you'd want to get a PC splitter like this so that only the headphones are connected with a TRS plug (some TRRS jacks don't play nice with TRS plugs).

Need a TRRS female to two TRS male adapter cable. Example: https://www.amazon.com/UGREEN-Headphone-Splitter-Computer-Smartphone/dp/B073ZDDTH2

Just use a TRS splitter like https://a.co/d/02xtN1Yf and a TRRS male to male cable like https://a.co/d/05QW9Jg2 Plug the TRRS cable into controller and the female side of the splitter then run the mic jack into one of the headphone outputs on the RCP2 and the headphone jack into one of the mic inputs on the RCP2. Assuming you don’t already have 1/4” adapters, here’s some https://a.co/d/0hYwsJ7i AFAIK this solution works both on Xbox and ps5 (although Xbox controllers sometimes require an extra control adapter for the controller)