I had good luck with waas boundaries before we got rtx.  I love using the headland pattern and it was usually off some, but was very lucky to be able to use it most of the time.

Here is something that I did learn about trying to use different corrections.  I was using a friends tractor that had rtk.  2 of my fields could not get rtk all the time.  I was running it using x-fill and then completely lost rtk.  So I changed the correction to SBAS.  It work fine if I kept moving, just like waas usually does.  The thing I learned was that when switching from waas to rtk was the lines were instantly off 3ish feet.  I ran 2 different lines.  One shifted and one original.  When ever I changed correction I used the other line and was right on.  It was also the same when I would try to run headland passes using rtx that were made with waas.  The whole field would be off about 3 feet east or west.  I assume that you need to use the correction source to steer that orginally created it.  That what I was experiencing.

I would recommend, based only on "my" experience, that you do boundaries in what ever correction that you are using with your equipment.