I would like to know what the answer to the following question so I can bring it when I get to level 6th.
I am doing a Magus with the kensai and black blade archetype. At 6th level when I get the Magus arcana I can also get the extra Magus arcana feat or would I need to wait till ninth?
Well you don't get a feat at 6 and at 9th level one of your arcana is replaced with a Kensai feature... But aside from the Arcana replaced by your archtypes you can always burn a feat to get a new Arcana that you are eligible to select. I'd suggest picking up one with your 7th Level feat if that's what you're looking for.
Ok, Blackblade alters your level 3 magus arcana
Kensai replaces your level 9th arcana
That means you get an arcana at level 6. But you don't get a feat at 6th, you get 1 at 7th. So at 6th you get an arcana and then at 7th you can get a feat.
