Yes absolutely, go for 27.3 if you have a Wifi 6 AP. Overall Wifi 6 performance is so much better compared to the 26.x series.
With regards to your channel situation, might be worth checking the RF spectrum view to see if other channels are actually better. Meraki's Auto RF does not enjoy hopping around unless there is an obviously better choice.
Finally, if you have enough overlapping coverage and 2.4GHz is hopelessly occupied, consider adding RX-SOP to your radio profile, but proceed carefully with that and with ample testing, as RX-SOP can considerably shrink cell radius.