What are the major differences between an Environment Administrator and a System Administrator?

There are a few, you can consult our help files for the full range.

Env Admin https://www.interfacing.com/help/epc10-webapp/12.2/en/topic/9-0-environment-admin

Sys Admin: https://www.interfacing.com/help/epc10-webapp/12.2/en/topic/10-0-system-admin