Hi,
I need help with vlan setup.

Need: any device that is configured with vlan 20 should get dhcp from vlan 20 when connected to any port on the switch.

Hardware: Mikrotik Edge router>> Traffic shaper Mikrotik>>Mikrotik Switch>Netgear Switch>>netgear switch

I am not sure if i should create vlan 20 on the bridge or downlink port to the Traffic shaper and then how to pass the traffic from first device to Netgear switch. Netgear switch is already setup with vlan 20 tagged on all ports and same with the last netgear switch.

Please help

Have a look at this excellent VLAN tutorial, it's got example with switch configuration.