Hope this is in the right section. I need some recommendations for flooring over radiant.
2x8 joists on 16in centers. 1 layer of 1/4in plywood and 1 layer of 1/2in plywood. under the plywood running between the joists as aluminum track with the pex tubing.

Now, as I understand it I cant do glue down over plywood. So what are my options for hardwood flooring. Can I do staples or nail down that wont penetrate beyond the 3/4in of subfloor.

I would go with engineered for it's dimensional stability over radiant heat.

Yes, glue down over plywood is acceptable. You can also install by nail/staple method into the 3/4 ply. Most engineered products are glue, nail, or float, but always check with the manuf. on the specific product.