I use one per container that requires one (containers are all about isolation after all) , but since I use Ansible to maintain my Docker hosts, management is really simple.

I have four primary VLANs, each with its own IP subnet:

1. Production - TV, media servers, family desktops, laptops & smartphones
2. Lab - my own space for learning & testing
3. Management - this is for host management (currently applies to physical hypervisor infrastructure)
4. IoT - this is for devices that like to "call home" - my printer is on this VLAN (I need to put the video doorbell on it too)

I have an additional three VLANs - two for work and one for the odd project I might find myself working on. I also organised my SSIDs to reflect their purpose: , .lab, .iot etc.