Questions about Stubby

I use Stubby, however, I have a vlan2.

When installing stubby it activates the option 'Ignore resolv file', and in vlan2 I have set the option 'Use custom DNS servers' to 4 alternative dns addresses.

Question is: When I activate 'Ignore resolv file' do I lose router cache on vlan2?

And what is the difference in the practice of the 'Use custom DNS servers' and 'DHCP-Options' options?

Custom DNS server is used for the OpenWrt for NS reachable from that interface. DHCP option 6 is the NS advertised to DHCP clients.
The "Ignore Resolve File" is activated to make sure your system won't query a resolver in an insecure way.