Mini-ITX isn't an issue in itself (look for builds in this size…), but it is limiting.
If you want Thunderbolt, only Titan Ridge (TB3) can be made to work like on genuine Apple hardware. So, with a single PCIe slot on mini-ITX board you MUST find a LGA1200 motherboard with on-board Titan Ridge—not Maple Ridge. Alternatively, you could take any Z490 board with a 10th generation CPU (NOT 11th!), use the iGPU, and put a GC-Titan Ridge AIC in the PCIe slot. If you can find the card, that is…
With 11th gen. and later, a dGPU is needed, so that takes the PCIe slot. I suppose one could use an adapter to drive a GC-Titan Ridge from a M.2 slot… but at that point it's better to just go for micro-ATX or larger: One will need at least two slots.
Without Thunderbolt, mini-ITX LGA1700 should be fine.
The need for proper USB mapping is general to hackintoshes, but is maybe higher for newer boards because newer chipsets provide way too many ports.