Question about /etc/resolvd.conf and local resolver

[J Doe]

Hi,

I had a question regarding configuring: /etc/resolvd.conf for use with a 
local caching resolver (using BIND), on the loopback address on OpenBSD 7.0.

This server is a mail server and I make use of DNSBL's such as SpamHaus, 
which is why I require a local caching resolver.

I see in: /etc/resolvd.conf that there are two options for the: options 
directive:

    edns0
    tcp

Because I have: /etc/resolvd.conf configured to use BIND on localhost, 
can I add either: edns0 or: tcp since I know the resolver on localhost 
supports this and it's the only resolver I ever contact ?  I am thinking 
that this is perhaps more efficient than using just UDP without edns0 or 
tcp.

The other thing I'm wondering is whether this is superfluous ... does 
BIND "know" when being queried over localhost to use better network 
settings that UDP ?

Thanks,

- J