vatw

There are lots of them out there.

For example passmark is one of many.

https://www.cpubenchmark.net/cpu_list.php

passmark

I just go find my CPU and use the number to compare to eBay listings. Is it perfect? No.

But it gives you an idea. Each site has some set of algorithms and they get a score for how quickly it can execute on that hardware.

Some of them they allow users to run their system and submit numbers so you get a better sense.

I’ve tried a few of the things you mention over the years.

However, I’ve lately gotten into the used business PCs. The performance of even a 6th get Intel CPU more than double an RPI4 or the ATOM in my NAS, depending on how you count. Sure, it’s quite a bit more power, and they have their place (RPI in the garage), but I’ve gotten a few SFFs that have room for multiple HDs for like $50-$60 shipped, as long as i’m patient, since I don’t care for the windows license.

The CPU benchmark sites are what convinced me that more SBCs was not the solution for me.

I also tell myself that i’m recycling what could have been ewaste otherwise. I am afraid to calculate the energy cost.

I might violate your top “ideal solution” checkmark, but I have a raspberry pi running Motion Project (https://motion-project.github.io) on site and it makes an easily viewable webpage-stream. My Rpi4 can handle 2-3 video streams, with motion detect-video-save, periodic snapshot, etc. etc.

Not for the feint of heart, but it is the way I solved a very similar problem. I’m using random mixed brand of IP Cams, whatever was cheap at the time.