I'm not sure what you mean by "rendering" exactly, but assuming you mean transcoding or conversion, the bottom line is that it depends entirely on how you're connecting the two machines and doing the playing.
1) If your NUC is connected to the server as a
library client, and you are starting playback
from the NUC, you're not using DLNA at all. The settings that govern what happens during the file transfer in this case are on the client (NUC) under Options-->Media Network-->Client options. If you choose "no change" for all file types then the server will not do any transcoding. If you choose transcoding, transcoding will happen, but I believe it happens on the server. If you want it to happen on the client, choose "no change" and then setup output format/DSP studio on the NUC to do what you want.
2) If you are starting playback to the NUC
from the server (i.e. pushing files) then you are using DLNA. The settings controlling transcoding are on the server under Options-->Media Network-->Add or Configure DLNA servers. You can create separate profiles for different types of renderers, and tell MC whether or not to transcode different media types. Any transcoding will happen on the server. Given that your NUC has a full instance of MC, you should not need to do any transcoding, so you you should create a DLNA server profile that is set not to transcode and then associate that profile with your NUC zone by right-clicking on the zone and choosing the appropriate option (I'm not in front of MC right now, so I'm working from memory).
To make the load on the server as small as possible, you should use method 1) for playback, and ensure that no transcoding is selected under client options on the NUC. For bonus load lightening, map the media drives on the server as network drives on the NUC in the same way they're setup on the server. The goal is to have the same path to the files on both PCs. Then make sure that under Options-->Media Network--> Client options on the NUC you have "play local file if possible" checked. If you do that the server instance of MC won't even need to stream the file to the NUC, the NUC will just use whatever network protocol is used for the share to pull the file across (the same way it would using windows explorer for example). That improves performance and places less load on the server, as the only remaining load is the load associated with the network transfer.
More info here:
http://wiki.jriver.com/index.php/Media_Server#Access_from_another_PC_on_your_LAN