Hello,
Taking a quick look I can see that you are using VLAN1. If you want to use VLANs on Mikrotik then go VLANs all the way, so create separate VLAN for 192.168.150.0/24 network and use it as trusted/mgmt network and your 192.168.20.0/24 network as your guest/client network. Then you can send those two networks as tagged traffic to your switch and then to your APs.
Also your pools overlaps
add name=pool_vlan_20 ranges=192.168.20.10-192.168.20.100
add name=dhcp_pool3 ranges=192.168.20.100-192.168.20.200
and “pool_vlan_20” is not used for the DHCP server. For what are you using that pool ?
Here are some links about VLANs in ROS:
Using RouterOS to VLAN your network
Tutorial: Home VLAN configuration (RB5009, cAP ACs, multiple SSIDs)