is main phase after draw step

Yes — the Main Phase begins right after the Draw Phase finishes.

The full Start of Turn order is: Awaken Phase → Beginning Phase (Beginning Step, then Scoring Step where you Hold) → Channel Phase (channel 2 runes) → Draw Phase (draw 1) → Main Phase (Rule 314, 316.1).

So the turn draw step is not between the Main Phase and the rest of the turn — it's the last thing before it. Also note the Main Phase is the only phase where you get Priority for discretionary actions by default (Rule 316.5.b), and your Rune Pool empties at the start of it (316.3, Rule 167).