The "print" size is not a layout setting. You select the page size in print setup. The page size that you select in print set up will determine what portion of your layout will appear on the printed page. Parts of your layout that are located too far to the right to fit on the page given current page size and orientation specifications will not be printed.
In layout mode, if you use print setup to specify a page size and orientation, you should bet both a horizontal and vertical line showing the print area on your layout for those options. items to the right of the vertical line will not be printed and objects below the horizontal line will be printed on the next page. You can also use preview mode to check to see how your layout will "fit" to the specified print options.
That helps. I wish there were individual print settings per layout but I'll deal with it.
You can create scripts that include the print setup you want and use them with the associated layouts. This, in my experience works well with Macs, but the Windows OS tends to forget what is in the script and just use whatever the last print settings were.
I have this issue with a group of people using a data base, so I include the print setup in the script (pausing it for them to reset as desired), then continue with the script. At least they don't forget to set it.
For a more precise, scripted control over the printing process, you might take a look at the MyFmButler plug in.