I've used these Rockbros sun sleeves for years:
https://www.amazon.com/dp/B07S345YRN...roduct_details

I find them definitely cooler than having direct sun on my arms. However, I live in a dry area so I think these work so well because they are good at spreading sweat around and then the evaporation cools. No idea how well they would work in a humid place.

Concerning sunscreen, consider using a mineral version. The brand I use happens to sell the more common chemical version as well. The packaging is very similar. A few years back I bought the chemical version by mistake and used it for a month or more without knowing. I eventually wonder what the heck is wrong with this stuff. It's not working as well, I'm hotter and sweatier using it. That's when I figured out it was not the mineral version.

I firmly believe the mineral sunscreens keep me cooler. They work by reflecting the sun. The chemical types absorb the UV and convert it to heat. Also, I assume the mineral reflect visible light which I don't think happens with chemical sunscreens.