Those are probably two of the most used methods, but certainly not the ONLY two. Most print-server devices support some form of LPR/LPD, so that's normally a good option. Others that come to mind:
Intel Netport devices used "proprint" on TCP port 2501, 3001, 3002.
VisionFS (Samba clone) uses "visionfs print" to hit printers shared on Windows PC's.
ICETCP (James River) has their own server process running on a PC which monitors a shared UNIX directory.
TinyTERM (Century Software) has something similar.
Unix to Unix can use "rcmd".
I used to know how to hit Novell print queues from SCO, but that's a memory best left behind.
I don't think one person could possibly list all the different methods of network printing.