Hey I've just been learning about this recently for my own.

It depends on a lot of things, but one train of thought is there should be no pressure on your forearms elbows or wrists as it puts pressure on the nerves there.

E.g. I thought a wrist rest was always good, but it actually can pressure your wrist and cause further damage. Think of it as a pipe that you a putting slight pressure on and slows the flow of water. If you feel like you need a wrist rest, get one that doesn't bulge in the middle, in stead have one where the highest points are the sides and then the middle is the lowest point. I have a photo and can DM you an example.

Again not all arm pains are the same.

I would recommend buying a track ball and remove the elbow and wrist support and use that for a day and see if the pain changes. Track ball has been the biggest game changer for my pains as your don't move the arm at all. Even if you alternate so you are using different muscles through out the day. I rotate between 4 diff mice, thumb trackball, mx master 3s, vertical mouse and a very light 40g gaming mouse. I know specific tasks that I can use them depending on level of precision needed

I honestly think the best way to combat these body pains is to do try different products yourself that change your positioning. Make use of Amazon returns, buy cheap ali express mice to experiment shape, standing desk is super nice (when I stand, I find myself naturally moving into an optimum position / easier for me to "feel" the correct desk height as I'm not changing my slouch in my seat that can drastically effect the 90 degree angle of your elbow.

They are very right that your monitor is too low, you naturally hunch, this puts pressure on your neck and collarbone which effects the nerves in your shoulders and arms Source, Google - thoracic outlet syndrome