If anyone's on Shunjou's last build (June 9, 2019), note that you might run into the issue of your Startup script mysteriously being wiped out upon router reboots. This is related to https://github.com/openwrt/luci/issues/2760, specifically in a commit on June 5, 2019: https://github.com/openwrt/luci/commit/1c09ee5e42550d6339bffa58d4cba3461948e19c
After commit 1c09ee5 using any of the web buttons in LuCI System → Startup erase all the content in /etc/rc.local
A fix was committed on August 21, 2019: https://github.com/openwrt/luci/issues/2760#ref-commit-7995ef3
Using Shunjou's April 20, 2019 builds will presumably avoid this issue: https://github.com/shunjou/openwrt-optimized-archer-c7-v2/tree/4943a2f01ac06b93e82c5b84ab01273f8f2f0d7d
Many thanks to @shunjou for providing these builds 
It is my build of choice on 5 Archer C7s I've set up for my parents, friends, and myself.