When I use my ISP's DNS servers and I am connected via OpenVPN the DNS trafic will not bounce through the VPN tunnel. When I use others' DNS servers will my DNS traffic bounce through the VPN encrypted tunel?
I'm assuming the typical setup that your VPN setup forwards all non-local traffic encrypted to the the VPN exit, i.e. all traffic to other systems in your local network will not be encrypted. I'm also assuming that the VPN does not come with its own DNS since you specifically ask about a DNS you've configured yourself. In this case the answer depends on where the DNS is configured and where the entry to the VPN is.
If your computer is the entry point of the VPN but you have DNS configured to be resolved by your router, then the DNS lookups will bypass the VPN, no matter if the DNS on the router forwards to your ISP's DNS server or to something else.
If the entry point of the VPN is your computer and you have your ISPs DNS configured on your computer, then the DNS will pass through the VPN and thus be encrypted. Note that even DNS lookups to your ISP will pass through the VPN unless you are directly connected (without cable modem, DSL router or similar) to the ISP, i.e. as long as the ISP's DNS is not in your local network.
If the entry point of the VPN is your router (i.e. router with VPN functionality) then all DNS lookups will pass through the VPN (i.e. encrypted) as long as the configured DNS server is not in the ISP's local network.