Myofascial pain syndrome due to iMac M1 2021

I have found that it can help to put something underneath the computer to make it taller if necessary so that you aren't looking down at it. There are stands you can buy for computer monitors to raise them, but you can also place books underneath. It might help to adjust it to a more comfortable height this way.

Based on your description, I recommend:

• Twelve South HiRise Pro Adjustable Stand for iMac and Displays.

That is the best option because it offers four height adjustments as well as internal storage with a professional appearance.

What Apple publishes on this topic: Ergonomics - Apple Support

The VESA mount is an option available at purchase on this iMac, so that won’t help here.

As has been mentioned above, you’re headed for a stand. Maybe also a standing desk.

I've been using something long before those stands were available - since I got my first iMac many years ago. A block of wood (a 2x2 or 2x4), covered with shelf contact paper, will do nicely. I now use a stand from the company suggested above.