Use the heavy portable corral panels
(the ones that weigh 600-800# apiece)! Don't invest in anything permanently installed in the ground. Take them wherever you want/need them, whenever you need them. Change the plan/configuration anytime you want to. Buy them new, and in 10-15 years, they'll still be worth nearly what you put into them... how many fixed position corral systems can you say that for?
Beyond that, I built a portable 28' double alley this year... not adjustable width, but since using it, we absolutely haven't seen a need for that... must have gotten the design right on the first go-round. Lanes are 29" wide between the rails, but then I installed double high guard rail along the bottom on each side of both lanes, so that gets it down to about 20" at the bottom. We've run everything through except newborn calves, and have never had a single one turn around in it... didn't even try. Not having it adjustable width then allowed me to put gates along the outer sides of each alley. Primary idea there was like if a cow would get down in the alley, I could get her out of there. And that works... but we found that they also come in handy for sorting, etc., too. I wanted this alley portable so I could take it to any pasture I wanted whenever too... My squeeze chute has wheels to go under it as well. On the back end entrance to the double lane, I make a Bud Box (12' wide x 24' deep) with the heavy portable panels and a few gates. Works great... I can pretty easily keep up loading the alley with three guys working the chute.
We normally only use one of the lanes, because I can easily keep up with the guys up front... so I just use the other lane for sorting off an animal that will need special care, to take care of when it's convenient, or like if I have a bunch of calves in the Bud Box after running the cows in, I'll load them into the other lane, and they'll let them out when they get to them. They don't interfere with the flow of the primary focus that way.
My point is, you don't NEED a double lane, if the lane is set up for really good flow. But a longer
lane, like I have, vs. what most have as a "portable system", is going to help your flow out alot more than a short lane, where you can only have one animal in the lane ahead of your chute. Using one side only, I usually will load 3-4 at a time into the lane, and I can have another two or three waiting in the "lane" made with the crowd gates in the Bud Box (the yellow gates in the pic below). The "flow" is always best if there's one critter in the lane ahead of them.... they just jump right in then. Slows it down a little if the lane is completely empty when you want to load it. So THAT'S why you want to have a lane longer than just one animal... and multiples of that is better yet.
We do embryo work, so we end up running the whole herd through a few times on each series... This whole thing gets wheels under it, and hauls like a trailer.