Our subfloor is plywood as a result of our home being above the ground.

Should we glue or nail down brazilian walnut?

Would you put down some type of moisture barrier or sealer? or felt paper?

Which adhesive is best?

Should we put down some type of sound barrier?

Is it solid or engineered? How much experience do you have?

It is 7/16" solid. I am completely inexperienced (I'm a 22 year old girl with absolutely no do it youself knowledge whatsoever), so I am having a carpenter install the floor. He wants me to tell him what I want.....nail or glue.....brand of glue......moisture barrier or not......etc.

I appreciate your help so much. I'm just really overwhelmed with all these decisions.

Thank you

I recommend hiring an experienced and licensed hardwood flooring contractor. It is possible to glue or nail that floor. Gluing will be more money. A vapor retarder is recommended to be installed on the earth in the crawl space if you have one per NOFMA specs.
https://www.nofma.org/Portals/0/Publica ... arders.pdf
BTW, no such thing as a "sound barrier". Cork can be utilized to reduce noise transmission but it's effectiveness depends greatly on the building's construction. If you want a "quieter floor", then look into a floating foor.

I'm with Gary this carpenter should know what is suitable. Pay attention, if he wants you (no experience with wood floors) to make decisions relevant to the flooring, wai,t can you hear that (bells and whistles) red flags. Be smart

Agree with the above.....and I would nail it down in your situation.