how much does the knot on a leader effect casting? does it get hung up on the guids?

not too much unless your using micro guides,

I don't like any knot going thru my guides, I use short leaders and swivels. When I do join line it's a least 75 yds so the knot doesn't come into play.

i use an albright knot to join leader to braid and never had a problem with them going through standard guides. i havnt fished a micro guide rod yet so i can comment on that...

i use an albright knot to join leader to braid and never had a problem with them going through standard guides. i havnt fished a micro guide rod yet so i can comment on that...

Same here; however, I've had some issues if I couldn't cut the tag ends well when retying on the water. I use better, surgeon's scissors now and see no issues.

Just need to make sure your knots are well lubed and neatly tied. Albright tends to be thinnest profile in my experience.

An Albright knot joining 65# braid and 17#fluoro will pass #4 micros with no problem. The Albright/Alberto is the slimmest strongest leader knot you can get