all this time i thought vader was second in command...smh

Actually

I didn't know that either

just doesnt feel right to me with vader being one of the most powerful beings in the galaxy at the time but whatever. it didnt really affect the plot at all.

So I started looking into lore and Tarkin was the only officer vader couldn't order around so rank wise Vader outranked Tarkin but tarkin could give vader orders

Tarkin did outrank Vader military wise, but Vader spoke for the Emperor, so he could give orders if he wanted.