On the issue of the pips/bars on the formal uniforms, I wish they would publish details.
Pike as a full admiral had four gold while Marcus also a full admiral had five, I presume because he was head of Starfleet.
Kirk and the other captain had four silver.
Spock as a commander had three silver.
Uhura, Zulu & Carol Marcus as lieutenants had two silver.
Chekhov as an ensign had one silver.
So these unlike the arm stripes follow USN rank insignia.
I am not sure about lieutenant commanders McCoy and Scott, McCoy seemed to be wearing three while Scott had only two?
As for lieutenant junior grade does it even exist?
Noel Clarke's character seemed to be enlisted.