You can’t have it both, as in, you can’t somehow have the upcoming ones sorted by whichever comes first without then also having all the past ones preceding them (it would be odd to sort the future notes in the inverse order with respect to how past notes are sorted).
The main idea behind Agenda has always been that future and current notes are at the top and as time passes they slowly “sink” to the bottom, becoming a timeline back in time, hence this being the default.