Well firstly if you can get into the OS then I think this thread has you covered:
I've created a windows 7 image from this thread using nLite, I intergrated drivers and all the current w7 updates at the time of creation:
Its doable but takes some spare time. Worth it for peace of mind. Although personally I have multiple installs of w7 (use the one on SSD, easyBCD can create a boot menu to chose OS drive (tangent install each OS as a single drive so it is bootable as a single drive not needing files stored on another disk)), and a DVD-RW copy but no backup on USB stick. I think if you got into trouble just ask in that thread, that forum has a very capable admin and users for this topic. As a side note, there is a program to batch download updates to 7,8 or 10 and then you just copy them to the correct directory and follow the guide. Nowadays USB would be the go to cause I'm sure not every pc comes with a DVD drive.
Edit: I'm confident you will find win PE as an option within nLite, also there is the opportunity to silently install programs i.e. HD tune. I never knew HD tune was more than a benching program.
Edit2: Your problem of " one of my PC's can't run anything newer than 8.1, the other can't run anything newer than 7 " will probably be unraveled by the good peeps on this forum. If I had to take an educated guess I would be looking at getting the right intel RST(e) drivers (assuming you're not on an AMD machine).
Have a look here (to get the most up to date windows patches before you install): http://www.windowsupdatesdownloader.com/
Edit (above link might be a bit of a chore this video maybe better, can't say either way as I'm in the process of doing it myself) :