The 1/4" line to the rear brakes allows a larger volume of fluid to flow to the wheel cylinders so the shoes apply in the least time. If you have rear disc you can switch the 3/16" tubing. Otherwise I believe it is best to use 1/4" tubing.
Also, these are really good and durable tools. They're expensive but if you plan to do more than one line it's good to have.
https://www.ridgid.com/us/en/600-ser...rument-benders
These are a little less expensive:
https://www.ridgid.com/us/en/400-ser...rument-benders