I don't do any percentage. I have always done a large wc once a month for 15 years. My total system not calculating lr volume etc is 210gal. I do a 35 gal wc once a month. Rarely twice depending on if something is a miss or looks test out of the norm
I change about 1g per day broken into three smaller changes. So I change about 30g per month. This is about a 50-60% water change for me as I have a 60g cube.