At the end of the day worked out great for me. Didn’t matter if I had a 14 hour day or 16 hour day. Strictly enforcing end of day OMAD was much easier for me than eating in morning and toying with my will power to wait it out until the next day.
I don’t know the stats on this but my take is this. Consistency with fasting is good, varied fasting times and calorie amounts is helpful for your body to avoid a plateau. It was for me anyway. If you can why not try a 20:4 on the days where you need a bigger window and Omad when you can make it work? I personally find it best to do 18:6 most of the time but once in awhile do Omad 20:4 and a 36hr when I’m able.
You have to make IF work for you and your schedule. So if these days don’t work for you, don’t worry about it. It’s okay to find another approach on these days.
So you can have different IF plans on different days if you need to.