You might have me on the which GPU is best for streaming - my testing wasn't extensive enough to prove much of anything other than what I had on hand, which wasn't every card available. In fact I'm going to make an admission: every Radeon I tested with seriously was built into a Ryzen CPU, not a stand alone card. The Nvidia card I tested with was a bit out of date (1080 Ti), older than the Radeon. I have a newer one now, but I've only done just a little testing with it - cold storage, not streaming, so I did not include it in my statement since I didn't get serious and measure it. I just know it did better than it's predecessor on a quick once over.
I most certainly am not wrong on every count. Consistently on multiple setups with every combination of CPU/GPU I've had available the CPU always makes the best "cold storage" files as long as you tune everything right. It might take a week to compress a 4K BRD in comparison to a GPU that knocks it out in a few hours, but in the end the file is tighter compressed with very similar quality, maybe slightly better.
I have tested on both Intel and AMD CPUs, multiple Bulldozer era, older Xeons, i7, Ryzen 5 4000 era, Ryzen 7 7000 era. None of the (older) Intel GPU's I've had available really support hardware encoding, I don't have access to a modern Intel GPU and I don't really plan on buying one since I tend to run AMD chips, and I have since I built my first 5x86 system in 96 or 97. I'll admit I suffered dearly for it in the K6/K7 era when the chips were great but most of the mother boards sucked and few that were good were nearly impossible to buy. (The Nvidia chip-sets stood out as awesome during this era, but that ended when they bought ATI). The answer is the CPUs all do about the same quality at the same settings, the main difference is more cores = faster job, and the CPUs always do better than GPUs on tightness. I really do want to find that GPU that can match CPUs in quality and do it with GPU speed, but I think that's just an innate trade-off for now.
End results:
If you're in a hurry or doing a live-cast - use a GPU.
If you're adding something to a long term storage library, like a movie to Kodi or even home videos to a server you're going to be prolific about stuffing videos onto, CPU.