Super Saiyan said:
Freeza had no scouter though, he raised his speed just to humiliate Vegeta.
Is Vegeta really that delusional that he couldn't tell how powerful he was when he went against Freeza initially?
Vegeta is powerful too... I would say that Vegeta is in part confident in his strength and partly confident in the SSJ legend. As you said, Vegeta didn't know what a SSJ was, he just assumed he was one because he is strong as hell! But against Freeza he's not so sure. Vegeta is not a complete idiot though, just see his change of reaction: before the zenkai he was terrified and after he received a zenkai he's more confident.
I like to leave Freeza Final Form ( Initial ) a little above Vegeta precisely in reason of the way the Saiyan treats him; Vegeta really seem to respect Freeza's power in the same way he respected his 1st form... and he didn't seem surprised by Freeza dodging his first blow. But as he still has a certain confidence (something he didn't have before the zenkai), I'd like to see Vegeta reasonably close to Frieza. P123 brought a good point, the gap between Vegeta ( pre zenkai ) and Freeza ( 1st Form ) should be the same as between Vegeta ( Post Zenkai ) and Freeza Final Form ( Initial ).
I have Vegeta ( pre zenkai ) at ~ 92% of Freeza ( 1st Form ), so this should be the gap in this case too.
Freeza ( 3rd Form ) 2,500,000
Vegeta ( Zenkai ) 4,600,000
Freeza Final Form ( Initial ) 5,000,000
~ True Initial Power ~ 7,000,000
Vegeta should be able to crush Freeza ( 3rd Form ) though... there are still people who believe that Freeza ( 3rd Form ) rivals Vegeta ( Post Zenkai ) lol.