- what's the source/destination quality?
- what's the container format? Quicksync doesn't support them all; even the newest gen is missing av1 and VP9 IIRC. But then, the same can be said for discrete GPUs.
- what filters are you applying. Many (most?) filters are CPU bound, which will kill you really quick.
But for supported formats without filtering, 12g Intel quicksync is regularly benchmarked at 4-6 streams.
One should always measure internet advice against one's actual use case. Personally I would argue that if you have a library of 8K video and more than 4 4K devices, you don't qualify as a "regular" home user. But of that's the case, hardware up my friend!
If you're ripping your own content and can ensure that everything is set up right so that the integrated GPU can handle it, sure, it will probably work.
That being said they could have made giant strides in this area on 11th-12th gen, I have no idea.
Other 10th gen I5 users get multiple simultaneous 4k streams going at > 1x speed. Even with tone mapping it should only use like 45% CPU for a single stream.
Unfortunately the difference between software and hardware development cycles means that when you're on data formats that came to prominence in the last 2 years, even the newest hardware may not support it yet.
Personally I moved from NVIDIA to quicksync exactly because I felt NVIDIA required too much babysitting. Driver compatibility, interactive mode updates, patches and patch compatibility... In comparison the intel driver felt like a cake walk. But you should definitely go with your own comfort level, especially for the price point!
This is on a headless box so thankfully I've never run into any of those issues, I just install their driver and pass the GPU through to my Docker container.
2) quicksync on a 10g or newer cpu is benchmarked at 4-6 4k simultaneous streams, but a lot depends on the details: container format in particular matters a lot, and so do your transcode options. Color matching for example, is only ever done on CPU. And IIRC AV1 and VP9 are not supported by quicksync (or older discrete GPUs).
That said, it's completely correct that you should measure all advice against your actual output device capabilities and source quality.
4k TVs are common, planning for 1080p use is a mistake at this point imo.