Carbon bars may have a profile unobtainable with AL bars which may increase comfort. But you've got to try them to make that call, which may be an expensive proposition. I have one bike with CF bars, but not worth the money to me. Part of the bar is really comfy, others, not so much. My other bikes have AL bars with gel inserts and padded tape. I have big hands, so bigger diameter really helps.

I'm all for going with as big a tire as you can run on your bike. I switched from 23's to 28's on my Scott Addict. They barely fit, but comfort and safety is much improved. I have 32's on my CX road bike.

Biggest potential improvement is bike fit and core strength. If you're not in shape and don't have fit totally dialed in, elbows and wrists can hurt even if you don't have arthritis.