OCG or CiscoU is more a question of your learning preferences. If you prefer videos, CiscoU is for you. Regardless if you use CiscoU or not, I would always make sure to have the OCG at hand.
But with "only" CCNA (don't get me wrong, CCNA is a great start, but SCOR is a beast) you will likely not have enough preparation with only these two preparations. If you have enough time, I would always recommend doing something like Security+ from CompTia to get started with Security.
And there is a great list of resources for the SCOR study on the Cisco Learning Network:
https://learningnetwork.cisco.com/s/question/0D56e0000CbR3YmCQK/scor-my-study-resources