Can I force hard passwords that my extra admins make for users? I’m looking at Webmin, Usermin Configuration, Authentication and I feel like I should be seeing a “Minimum number of characters =” and “Password must contain number y/n” “Password must contain capital letter y/n” etc somewhere but I don’t see it.
You’re looking in the wrong place. Users are a system thing so you need to look at the System Users and Groups module configuration (Webmin has users, but they should authenticate with system users, whenever possible, and they do for any Virtualmin user, except resellers which are only Webmin users).