^You can still play if you are careful and follow a regimen. One of the areas that causes arthritic pain or development in playing guitar is not properly stretching your hands and arms. It also does something to do with not properly warming up with proper guitar exercise before hitting whatever routine that you go through when playing. You have to treat it like a sport where the athlete warms up before they go into their main routine. I read that certain fingerboard radius and neck profile can cause wrist and finger pain and can lead to arthritis over time. A rounder radius like 7.5” and a big neck profile like a baseball bat could be detrimental. If you go down to a flatter radius from 12”-16” and a smaller profile, that would help alleviate any wrist/finger/hand health conditions that would rise up in the years of playing.Thank you so much for sharing your guitar building journey! I've always thought it would be cool to build my own, but just didn't/ don't have the means. I played one for many years until arthritis got me a few years ago & during the pandemic I discovered the uke, and I'm in love! It's alot easier for me to play and I've fallen in love with playing again! One day I will get me an authentic Hawaiian made one! One again thank you for sharing! I've enjoyed reading about your build!
Action plays a role too versus high relief and low relief. High relief means that the distance between the underside of the string to the top of the fret has a greater distance which requires a lot more effort. Low relief means the distance between the underside of the strings to the top of the frets is closer distance which requires less effort to chord and fret a note.
I would go to a store and play as many size necks and fretboard radius available. Pick the one that feels the most ergonomic and comfortable to you- their like shoes and you have to find the proper shoe fit to maintain balance and comfort. My 2 cents and I have been playing for over 35 years and I do those steps above so I can continue on playing.