Our Windows domain is far away. DNS performance is affected. Would it be possible for Windows clients to carry out external queries through an alternative DNS server directly? I understand this is not generally advised.
SnapOverflow
No, the conditional forwarder are configured on the DNS server side, not on the client side sadly
I would deleguate a local server with a DNS role that could redirect to the remote DC all your domain resolution, and resolve all other locally.
You can create a custom hosts file for each client that needs to authenticate with and/or use internal resources.