Try as I may, I keep coming up with different answers. Help.

I'm putting a sub panel in a new detached garage.
There is no phone, water, gas, etc to the garage. Only the electric for the following:
2-20 amp circuits for receptacles, 1-15 amp circuit for lighting, and 1-15 amp for a garage door opener. Nothing else will go in.

I bought a 60 amp sub panel with 4 slots (no main, just 4 slots).

I was planning to run this from a double 50 amp breaker in my 150 Amp main panel.
Total distance from main to sub is 55-60 feet, buried in pvc conduit.

I was going to pull 4-#8 thhn, one being the ground and set two 8' grounding rods 6' apart at the garage.

I'm in Calaveras County, California.

Questions are:
Anything in this not look proper for current code?

Can I use #6 THNN or stranded cable for the grounding rods? I can strip it bare, or does it need to be solid wire or a different gauge?

Also, does the ground wire in the conduit need to be #8 also?

Thank you in advance for all your help.

Yes, #6 is the minimum size to use, you do not need to strip the length of it, you do not need conduit unless it is on a wall and can be damaged.

You can get away with 3 #8 THHN/THWN and one #10 THHn green for the equipment ground.

Be sure your THHN is also rated THWN, which most is dual rated.

THHN only cannot be installed in a buried conduit as that is a wet location. THWN is rated for wet locations.

Otherwise you plan is fine.

Please remember to keep the Neutral bus and the ground bus isolated from each other at the garage panelboard.

Also, you cannot put both Neutral and Ground wires on the same bus bar.

I'll keep the ground and neutral separate in the sub panel. I bought a separate ground bus to go in the panel, No bonding.

Thanks for your help.