OK what I think you want to do is on the Id go into Options and turn on media Network=>check Use Media Network to share this library (you won't be sharing the library of the ID though). You probably want the authenticate option checked too.
Then, again under Media Network, click advanced and check ONLY the DLNA Renderer box. This way on the server machine it will show up as device. In JRemote you can the select this so it can be used as your Control Point for the Id or the control point for your main machine. You could even link the two outputs to playback at the same time.
HOWEVER, you might not want to set this up this way. You might want to use the Id as the server. Running both PCs as servers usually requires 2 separate libraries and I wouldn't recommend that. Each JRiver install though can be either a media server, renderer, or controller -- or all three. So this might not be your "final" configuration. You have a bunch of options here.
With 2 machines, basically one runs a server and must be turned on all the time (or WoL -- configured to wake up) it accesses either local files or external files like from a NAS. The other runs as a client which can do most admin/retagging etc to the server machine's library. Remember that modifying creating Views, moving renaming files, importing, and cover art stuff have to be done on the server machine (or using a remote desktop app from another machine if running headless). This might influence which machine runs as server too. Zones linked to output devices are not library based, so each machines audio for example and be configured per station.
Using JRemote or another remote controller, one needs to load a "server". You can have multiple servers, but usually as I said you don't want to. So the choice depends on you, and how you playback your media, ease of access etc. You can also do the initial setup using PC1 as the server and PC2 as the client for ease of configuration, and then change your mind (probably entailing restoring a library backup file) Your choice might have something to do with the fact that the Id is in Linux and so doesn't have Theater View. However it will function very well as a renderer for audio, and consumes like nothing in terms of electricity and has a small form factor.
Regardless, not knowing more about your listening areas and such I'd try my suggestion first, then once you see the plus and minuses in your home, you can change it to fit what suits you best
Hope this helps
PS- it can be helpful to set IPs via the DHCP option in your router to avoid some network issues you might have, and do port forwarding for external access too. but that goes a bit beyond the "purview" here