Just out of curiosity - - - is it just for physical embellishment (painted)
or to look pretty and varnish it for the aesthetic appeal ??
Will it be kept under cover or in a garage/carport ?
Posting a photo or two with some notes of exactly what you want to do will help a lot
with more educated responses.
I myself, am a "wood purest" . . . meaning that on nice boats, teak or mahogany, oiled or varnished.
painted could be the same or any good exterior wood. WEATHER will kill any finish on wood just
due to the wood's characteristics of expansion/contraction .....
White oak will work well if not painted. IMO, red and white oak does not hold paint well outdoors.
If painted, just follow the procedures of painting the wood trim on your house.
If varnished with SPAR varnish, stand by for heavy rolls to starboard !! LOL
meaning every year, sanding, patching and revarnishing.
Just looked over your build you have posted and you are doing one jam up job of it !!!
for the "maintenance free" aspect, you could use any of the PVC materials available at your Big Box Stores.
I lived in Nicholas County, Summersville, for 3 years and loved it up there !!
So I know a little bit about your area. I do miss the mountains - but - not the minus 15* winters !!!