"Will Kodi or SPMC have issues detecting this NAS on the network?"
Not sure I understand your question - "detecting" as what? responding to IP address you entered, detecting as DLNA device, something else? As others said, you can use NAS as storage (have the client run elsewhere i.e. running SPMC on your Shield and map NAS shares into your libraries). I use that setup and SPMC has zero issues with this. Also zero issues when accessed from other Windows/Ubuntu computers. You can also use NAS as the media server by installing DSVideo, DSAudio, DSPhoto set of packages from within Synology OS if you want to turn it into DLNA device and stream to fixed/mobile devices. All works. Or you can use a third option where your client would run Plex client pointing to plex server which in turn has NAS shares in its library. Also zero issues. I have had shares accessible primarily over SMB and later switched to NFS shares and run this in exactly that set up for everything other than pictures (SMPC for pictures) , Nvidia Shield runs plex client, separate server runs PLEX server, NAS hosts the files, Plex server automounts NFS shares as startup. Everything works and works well. very happy with DS216j
"Can it handle streaming blu-ray bitrates if my network had enough bandwidth?" Why wouldn't it? the actual network requirements are significantly lower than gigabit port built in. now if you want to transcode multiple 1080p streams at once AND you want to do it on the NAS (why??) , then yes, CPU may be heavily utilized (see above).
Other all, great device - low power consumption, good ecosystem, very easy to use.