I've also thought perhaps using the Meraki Go switch and trunking that back to my test 9800L. My understanding is the Meraki Go Router is capped at 250mbs for whatever reason. My consumer router can easily push 800-900mbs from my ISP.
The Meraki Go switch and MR42 will create VLANs and segment your layer 2 network, but each VLAN will require a router and a gateway interface in said VLAN to actually reach the internet. That netgear router needs to do that bit.
For example, let us say you have 10 devices on VLAN20 all using static IPs in the network 192.168.20.0/24.
What is their assigned gateway IP address for the internet? It should be the netgear router, and let's just say that is 192.168.20.1 for ease.
The netgear router would need to be able to have an interface in each VLAN in order to provide each network a gateway to the internet. It would need, for example, another interface in the Guest VLAN30 and yet another in the management VLAN10 in order for those networks to reach anything in another network (i.e. routed).