It doesn't matter which way you do it, the end result is the same. Do what makes sense based on your best guess of your MAGI. As long as you timely file your tax return or request a filing extension, the deadline to recharacterize an IRA contribution made for 2020 is October 15, 2021.
You could also just wait to make the contribution until you know your MAGI. That would mean that you would miss out on any investment gains or losses between now and then. The deadline for making the contribution for 2020 is April 15, 2021.