What is the difference between an agent and non-agent of an EMI in Europe/UK?

There are a couple of differences between an agent and a non-agent in the European EMI licensing regime.

A non-agent for starters is commonly referred to as an operator-led model. Where the operator of the license is handling all the facets of custody of funds, compliance, reporting, etc. The non-agent is essentially responsible for marketing & sales, including the first level of customer support.

For an Agent led model, there are essentially two: 

1. EMD - Electronic Money Distributor, and
2. RA - Registered Agent

You can see a detailed comparison I did on this earlier on at: https://faisalkhan.com/delegate-status-comparison-table/

The main difference between the two is that an EMD can only resell the services that the principal EMI is offering, whilst an RA can create new products/services that the RA can sell, with the approval of the principal EMI.