Im trying to set up OpenWrt in AP mode. From what I gathered OpenWrt does not have a AP mode but can be used in AP mode of DHCP and firewall is disabled, is that all I need to do?
You do not need to disable the firewall, but you should absolutely disable the DHCP server (not the service, though).
Why should I not disable the firewall? In my case im using it with a pf sense protectli vault so I assumed it would do more harm than good to have it enabled. Do you think I should enable it?
It isn't that you "shouldn't", but that you don't need to. The firewall consumes minimal resources and doesn't need to process any packets when you're operating the device as a bridged AP (since everything flows at L2). The only real purpose of the firewall at that point is to govern the management of the AP itself -- leaving it enabled in a known state will ensure that it is always reachable as desired. Sometimes people will change the name of the management network (default lan but if it is changed, it could be anything), but then forget to add that to the lan firewall zone. If the firewall was disabled, they'd have access, but as soon as the firewall is re-enabled (for any reason), they get locked out.