The easiest to hack with everything working is the Haswell models. I have a HP 800 G1 with i7-4790T (2.7ghz 4C/8T). That was a good deal. I have also a HP 800 G2 i7-6700 (3.4ghz 4C/8T). But like you I have never got sleep to work. Not really on any Skylake cpu. Too bad because the HP 800 G2 is a really fast hackintosh. At least 30 full tracks in Logic X. I think the Coffee Lake models are now the best price/performance and everything works on my Lenovo m920x. I have the non-T version
i5-8500 3ghz with runs at 65W and beats the i7 T-version! Still I do not see the fan blowing much. The Coffee Lakes are not as easy to hack as Haswell but with
@deeveedee fantastic post I managed it. These mini-PCs with Radeon RX560 sound great but I never tried them. And remember they all use T-versions cpu. I also read they run hot and I want small and quiet! If you are looking for something small with GPU performance, make an ITX build. My dream mini-pc would be a i7-8700T or i7-9700T. They do not run hot. Or the i5-9500. But those models are rare and not easy to get cheap. So answer to your question is maybe Coffee Lake models
You can replace the CPU with an i7 from Ebay but it is cheaper to buy an i7 model. I upgraded a m93p to i7 but then I got the box almost for free.
Look at these alongside each other and you see.