I'm with Iddee, either way will work. Does your undrawn frames have foundation or not. If foundationless, you will need to keep a check on them to make sure they are drawing it straight. I would put them in one box and add the other when the first is about 80% drawn. I have let mine draw brood and honey supers that way, half drawn and half foundationless. Good luck to you and your bees Tiger.
They're all foundationless. Overall, last year the bees did a good job building straight comb. I had maybe 6 frames that they started building "wonky comb", but I caught it and straightened it out before it became an issue.
From what I understand, bees will draw out frames faster in the brood box, which by checkerboarding empty frames in with drawn frames, they'll have those filled out pretty fast. and then by rotating the outer frames up to the next box. Then putting two empties in the middle with a drawn frame between them, they'll draw those frames faster than just leaving them in the top. I couldn't do that method last year. I was using a single deep because that's how my nucs came, and the queens never left the deeps.
Even after the deeps were packed with bees, brood and honey, they weren't building comb in the medium. One of the hives had a broken frame, so after most of the brood emerged, I cut the comb out, split it in half lengthwise and put each piece into a medium frame with rubberbands. Four days later, one hive had the frame completely draw and was working on several other frames. The other hive had the piece attached and was working on completing it and was working on another frame. Both hives also cut the rubberbands for me. :)