21:3 ?
Yes and no? It really comes down to what you’re consuming. Little to no carbs? Are you at a caloric deficit? No matter the eating window you can slam a ton of calories so it’s a two prong problem. Longer the fasting window the more weightloss but depending on what you’re actually eating is definitely a part of that
23:1 would be faster and more weight loss. You’re fasting in a longer window so would be in ketosis longer. Also, it’s hard to eat a whole bunch of calories in 1 hour as opposed to 3, so you will most likely eat less with 23:1.