Depends on what is inside, intel N100 or better CPUS are considered really good in general. There are some bad CPUs in mini-PCs though. Make sure the hardware has drivers for your choosen OS, not everything supports linux [well] even today. And every once in a while someone makes a PC with bad design and so it doesn’t work well for technical reasons.
There are a lot of small PCs that are low power that will work well. I haven’t used GMKTech’s, and one look at their website says I won’t try to navigate that mess. (why does everyone need a subscribe to our newsletter popup blocking my ability to see anything - I avoid anyone who abuses me like that)
How small? I bought a N100 system from Protectli which I’m happy with. It should work better than a pi according to the specs - but I never tried a pi so I can’t say if it really is. However this is bigger than a pi. I have an old system76 Meerkat, which is much smaller (I think this is the NUC form factor?), but my system is 8 years old and so not really comparable to anything modern, but that is an option.