I’m your weight and have been riding for 25 years. With regular volume tires (around 2.3-2.4 width) I’m around 30 in the rear and 3-4 psi less in the front. You have to keep in mind you need a certain pressure just to support your weight (all other factors coming secondary to this). If you find that you’re having issues with traction or tire squirming I’d look to the tire itself after you figure out what pressure is good for your weight and speed. If you need more then 30psi then you need a stouter tire (heavier duty casing). People that are running near 20 are either light weight, not riding aggressively, on high volume tires or all of those things. If you ride hard and fast over real terrain (with 20psi) and weigh over 200lbs you will blow up your wheels if you can keep the tire on the rim long enough to allow it.