Since you have a solar rights law in your state I would suggest that you first read and understand that fully as well as your pertinent HOA rules. Is there a conflict? What are you required to submit to the HOA for the solar project?
Having reviewed the AHJ and HOA requirements, decide whether you want to stay with your 40 ft setbacks plus fencing or vegetation, or redesign for the 50 ft setback. As someone else has mentioned, remember the old adage, good fences make for good neighbors.
Your submittal will need to meet all the HOA requirements except when they conflict with state law. It will of course also need to meet all of your AHJ's requirements.
I would not open things up for additional review by requesting a variance except as a last resort, and it seems that you're not in that position. It sounds like you can install what you want two different ways without a variance so why would you be granted one? The variance process also includes community review so you'll be granting power to your neighbor(s) which he (they) doesnt (don't) have otherwise.
Check this but I suspect that the HOA rules will already require you and any future owner to maintain the vegetation or fence so maintenance concerns shouldn't be an issue.
Finally re the neighbor, once you have AHJ and HOA approval, then politely let him know you are proceeding. He knows (or soon will realize) that you can do this without his approval.
By interacting with him further during the planning process you are encouraging his preception that he has decision making power which he doesn't actually have. Continuing to interact with him under those conditions will only make him more frustrated. No one likes to have their power taken away from them, even if that power was an illusion in the first place.
He's going to be frustrated for awhile either way but by waiting till the end to communicate with him you will actually be reducing his frustration overall rather than increasing it.