I made the mistake (LOL) of looking at the Shimano Compatibility Charts. Until today I did not know these existed. However, looking at them only made me more confused.

I have two 10 speed chains on hand and Sram PG-1070 and a Ultegra 6600. Both 10 speed.

Now, if I am going to build a Space Horse with 10 speed GRX what 10 speed chain do I need?

So I consult the Shimano Compatibility Chart. I think it lists 7 or 8 chains - most begin with HG (so I assume hyperglide) and two that don't start with HG but if you look them up they are HG too.

So I suspect that rules out the 6600 Ultegra Chain since I think Hyperglide is MTB not road. I don't know if the PG-1070 is HG compatible.
now that

I am not sure that I improved my life by looking at the compatibility chart - I might have been happier with just installing one of the chains (probably the 1070) and calling it good. Now that I know these chart exist, I am going to feel compelled to look at them - perhaps ignorance is bliss.

So is either of the chains I have - perhaps the SRAM 1070 hyperglide compatible? Or do I just spend 25 bucks for a HG chain and sit the two chain I have back on the storage shelf? LOL