Post length?

You could share a mortice with the brace and girt, otherwise I try to keep them 6" away. I use 3" long tenons and 1, 3/4" pins on the ends of girts. I don't use a lot of half laps, I find a simple mortice is just as or quicker than lap joints. If the lap goes all the way across the member than you can saw and chop it out, thats quick and efficient.

Can you install the girts as it goes together or do they need to be installed after the post are up?

Tim