One thing that we can be pretty sure about is that the insignia systems in the pilots were different from the later OS. In "The Cage" Number One (called lieutenant) and Pike wear the same insignia, whic doesn't make sense unless you think they hold the same rank.
It's perfectly possible that they do, at least in terms of substantive rank (this isn't uncommon on large or mid-sized warships in the RW) with Pike holding the title of Captain by virtue of being the CO. However, I prefer the idea that (in-universe at least) Pike's single stripe is an error (possibly he'd run out of clean shirts due to the difficulties on Rigel (?) and had to use an old officer's shirt?) and that he should have been wearing the same double braid as Kirk did in WNMHGB with the rank of Commander and the title of Captain.
Garrison, named a chief petty officer in the scripts, wears a voided, ladder-like stripe, never seen again. In WNMHGB, lieutenants and lieutenant commanders are shown to wear the same single stripe. Not to mention the fact that the shirt colors and badges were completely different than those later seen.
Personally, I think we should have seen CPOs again (but that's a slightly separate topic) and similarly to above confusion between lieutenants, lieutenant commanders and commanders wasn't unusual in TOS either (in TOS: The Alternative FactorI, Assistant Engineer Leslie (a Lieutenant) was Duty Officer on the Bridge with an unnamed Command Division Lieutenant Commander serving at Navigation (a second unnamed Command LTCDR, this one a black man, also appeared in a senior staff meeting during TOS: The Enterprise Incident).
Also, while background material might have suggested that Number One was a Lieutenant Commander (Spock's later rank might suggest this as would Mitchell, who is refered to as a LTCDR), the script refers to her only as Lieutenant, which wouldn't be inconsistent with her being an XO.