Passing options to Bro plugins from a file

I'd like to read options into a plugin such as IP addresses, hostnames,
ports, etc from a configuration file. Looking at the redis plugin for
inspiration, it looks like I could set types in the bif, set initial
values in the plugin's init.bro and then redef in local.bro? Is this
correct? Am I missing anything?

For example I'd like to have a bro script that can call a function from
scriptland to shove data into external DB. A use case may be something
such as writing time series data directly to InfluxDB. Instead of hard
coding the IP, port, etc into the plugin I'd like to be able to specify
the location in a file. I might also use the file to define a tag
structure for InfluxDB.

Yes, correct. It's kind of the "normal" Bro way: you define a set of
global options with defaults through the bifs and people can redef
them as they need to. A few of the plugins do it this way, another
example is dataseries/src/dataseries.bif.