Overclock-wise: the Aorus Ultra & Pro have a tried and true power design 6 PWM phases to 6 doublers driving 12 International Rectifier (IR) powerstages and is cooled by a massive fin-stack. The Taichi is using a similar 12x powerstage design but the Vishay powerstages are cheaper and have less monitoring/feedback features (this doesn't matter that much). The Pro Carbon is using 10x powerblocks (high+low side mosfet combined) instead of 12x powerstage that integrates driver+high+low side mosfet. The power delivery is covered in plastic and there is no heatpipe connecting the two power deliver heatsinks.
--> memory should not be an issue since AMD stated 3600C16 is the optimal memory.
Connectivity: All of them have Intel 1GBe LAN + WIFI 6/BT. All have USB 3.1 gen 2 type A and type C.
---> Aorus Ultra/Pro and Taichi have USB 3.1 gen2 front panel header , Pro Carbon has USB 3.1 gen 1 (aka USB 3.0) front panel header
Audio: All of them have ALC1220 audio but Aorus boards have WIMA caps (ALC1220-VB also might have additional features) and the Taichi has the TI NE5532 amp.
Storage: Storage-wise the Taichi has 3x M.2 and Aorus Ultra has 3x M.2 (Pro has 2x M.2). Pro Carbon has 2x.
Troubleshooting: Aorus Pro and Ultra have Qflash+ and dual BIOS , Pro Carbon has Bios flashback
Niche features: Aorus Ultra & Aorus Pro have Quad SLI support , Taichi has Quad SLI , Pro Carbon has no SLI support