I flew EWR-OSL which left about 75-90 minutes after the CPH and ARN flights. I got to the lounge around the time of final calls for two flights and it was downright calm in the lounge!
Side note, regarding the TSA/Terminal C question: As I have previously, I went through security (pre-check) at C and bussed over to B in order to avoid the mess that is B60-B68 security. Ive made the mistake of going through security a B before, not again.