It will need a JRiver person to comment I think to clarify what's going on, as I think there are several things conspiring here, but here are my thoughts.
It may well be that MC doesn't allow you to connect to one of its own DLNA servers. There's no point really, because if you've enabled DLNA server on a PC, it's also automatically an MC library server (because you've had to turn on Media Network). I don't know if this is indeed how it works and whether there is a way to hide and unhide MC DLNA servers from the list. But you might as well just download the library server's library, rather than the DLNA one. DLNA server does allow you create multiple servers with their own libraries so I guess it's possible you might want the ability to connect to a different library, but you wouldn't get different views as you have set up in the DLNA server, which is the only advantage of different DLNA servers, because MC is a sophisticated DLNA client and it ignores the views set up on external DLNA servers and creates its own depending on the views you've set up in standard view.
DLNA servers also allow you to specify different transcoding options and DSP which happen on the server, not the client, and this is why you want to do it that way. But I think the transcoding options don't work from the library that you are playing from. It's dependant on the renderer you are playing to. There was a longstanding problem in that MC originally only used the transcoding settings of the first DLNA server in the list but I believe there's now an option where you can associate a DLNA server with a DLNA renderer. So basically, you set up a DLNA server with individual settings for each renderer then associate the renderer with its appropriate DLNA server. Then when you play to a renderer, MC will use those setttings. It's not dependant on the library you have loaded, which literally only gives you the list of files to browse.
So I think what you need to do is connect to the library server as normal and then set up all your clients as DLNA renderers. But again someone from JRiver should confirm.