Well, macOS doesn't really have install options anymore (unlike the Classic Mac OS days), so there's no way to do a minimal install. There's just the default install, and it'd be really tricky to know what is safe to trim down from that. Probably better off to leave it as-is.Recently I've been wondering about minimal OS X VMs on Mac Pro-hosted ESXi instances. How small can one go...?
Most hypervisors can support sparse disk images, so that would be your primary way of not using more disk space than you have to. An install of macOS Mojave would take about 12 GB. macOS doesn't bloat up the way Windows does (due to Windows SxS), so your disk usage after that would be dependent on what you install and add to it.