RealcumberScripts Thanks a lot for your time and feedback! Really appreciate it.
Just wanted to reply here if it might help someone else. I got the official cable and that helped with the connection to the PC VR. Still experienced some stuttering. After finishing my build of the SR6 and getting things up and running though, I did some more research and eventually found out that my CPU (at the time AMD Ryzen 7 5800X) and RAM (at the time being 32 GB CL16, 3600 MHz) were actually bottlenecking my GPU (NVIDIA GeForce RTX 4070 Ti). After upgrading to a slightly more workload-heavy CPU that still fit my motherboard (Ryzen 9 5950X with double the cores) and doubling my RAM (still 3600 MHz CL6) I got rid of the stuttering completely.
In short, I found that the PC VR app and video playback of SLR through DeoVR is actually very CPU and RAM dependant than I thought. This is just an estimate from too little data to be definitively representative, but my GPU seemed to be only half of the equation. To some people more tech/IT savvy than me, that might be obvious, but if it helps someone out there, struggling like I did for a month or so, that's good.
