What are the differences in these two approaches, does that mean the supplier EPR system would have the option to code against the MESH API ? are these MESH APIs available in all languages ?
with MESH Client, does the EPR sends the documents using REST to the locally installed MESH Clients ?
The MESH API is an alternative mechanism to the MESH java client. You would typically use one or the other to access the MESH service, though I guess there’s nothing stopping you using a combination of both mechanisms.
So your EPR can either access the older file folder based mechanism or use the REST API.
If by “are these MESH APIs available in all languages?” you mean programming languages then yes. It is a REST API so any language which has support for https can use it.