This is my pass side which wasn't bad other than a 2" x 1" area centered between the top studs. My drivers side had a bunch more rot so the tacks are in different places to match the good edges of sheet metal I left behind.
I'm a decent "hobbiest" welder but not underneath a car and in the dark half the time. You can tell exactly in which order I put my patch panels on the car by how boogered the welds look. This was in the middle of the job so not too bad. By end my welds were looking pretty good.
I lapped everything and used a flanger on the edges so the panels look pretty nice for being non-stock pieces. I will only resort to butt welding on things the naked eye can see readily - some people may say that's doing it wrong but this is a lot simpler for me, given my skills, and I think this is stronger than the pinholes and mig wire strands I'd leave everywhere trying to butt the panels.