multisite subdomain behind reverse proxy

I'm trying to run a wordpress multisite subdomain setup behind a reverse proxy to look like its sub directories.

So the setup is like:

www.mydomain.com/articles --> cms.mydomain.com www.mydomain.com/news --> news.cms.mydomain.com

I've found there are many places in database and config to set domains/urls and am confused about which should be set to what you'd see in the url, and which should be set to the actual domain where WP is running.

Places found:

wp_options table
siteurl
home

wp_site table
domain

wp_blogs table
domain for each site

wp-config.php
COOKIE_DOMAIN
DOMMAIN_CURRENT_SITE

Any advice greatly appreciated. Whatever I've tried so far seems to work in some cases and not others (i.e. sometimes i get 404s on css, sometimes i get 404s on wp-admin)