my 20x30 plans call for 4x6 bracing from the post to the beam
in the plan it calls out 1/2" lag screws to connect the brace to the post and beam.
I was going to use ring shank nails for this, I can put multiple nails in contrast to the screws.
would this cause a future problem?
Sure, use lots. 6-8 is about equal to a lag.