Yes, it will work. You can still mix vlan-less and vlan-tagged networks, e.g. in hostapd.wpa_psk:
00:00:00:00:00:00 homepassword
vlanid=123 00:00:00:00:00:00 guestpassword
The lines that do not contain a vlanid parameter will not use a vlan and those clients will be connected to the interface you specify via the regular network parameter, just like in a regular radio setup.
Importantly, for mixed vlan-less and vlan-tagged operations you need to set the dynamic_vlan option to 1, like in my example above (0 means no vlan-tagged radios, 2 means only vlan-tagged ones).
("without isolation" is not completely correct, though. vlan-less networks are still separated from vlan-tagged networks.)