what is the best way to access configuration files for your own daemon?
Should I use uci?
you could use uci functions or access using filepath /etc ... I encourage to use that location in order to have your files backed up when you do a configuration backup.
If you're creating an init script to pass parameters to daemon, check out the code of something complex, like
/etc/init.d/dnsmasq or use this for reference: https://wiki.openwrt.org/doc/devel/config-scripting