Which Groupset?

I’ve only just learned this.
When the original 12 speed DA press release came out, I was sure it said something about the Cassette still requiring a new type of freehub body. I’d assumed the same was true for 12 speed ultegra, but good to know that’s not the case.

I’m wondering what the difference in cog spacing between 12 speed shimano road and road axs is?

There is a small difference in the cog spacing in the 12 speed mtb stuff versus eagle axs. But in use it doesn’t seem to impact it. Like Skinny, I use a 12 speed shimano mtb cassette, chain and chainring with an mtb axs mech and it shifts better than a complete eagle axs set up.

But the road axs stuff uses a flat top chain that might not mesh well with shimano 12 speed, has anyone tried this yet?

Using an axs road mech with shimano cranks, chain and cassette is of course an option

Unfortunately SRAM muddies compatibility between road/MTB due to the flat top chain they use for road.

If you want to mix Sram AXS derailleurs with Shimano drivetrain you need to use SRAM AXS Eagle MTB derailleurs - which is less ideal if you want to use on a road bike.