Looking for help understanding clock usage in my system

I should say up front that I don't completely understand how external clocks work (I understand the basics).  I'm currently using a LYH ock-2.  It's connected to a Gustard U-18 ddc, Gustard X-30 dac, and a Gustard N18 pro ethernet switch.  The LHY has three 10 mhz outputs in sine wave and three in square wave.  I've tried both and prefer square wave.

The ddc is connected to my Innous Zen Mkiii streamer by USB and connected to my dac via i2S.

I have recently purchased a Gustard U-26 ddc which should be a notable upgrade to the U-18 ddc.  Because the U-26 has a better clock, I'm wondering if I'll even need the LYH ock-2.  I'm going to try it both ways.

Here's my question....If I don't use the LHY ock-2 with the ddc and/or dac, would there be any point in using it at all?  It could be connected to the N18pro ethernet switch.  

Suggestions/advice would be appreciated.