For all-leather, stitched boots (think Nick's or White's) I go with Obenauf's Heavy Duty LP. It does a damn good job at repelling water and preserving the leather. You want to take special care around the "hinge" of the boot right behind the toe box. Fine sand and dirt can work its way into the leather pores and cut up the leather. You will get deep cracks in the leather which will cause an early death of your boot. Make sure to clean off your boots every time you take them off.
For any boots that are bonded with adhesive (like the rubber rand on your Lowa's or Kenetrek's) I go with the Kenetrek boot wax. Apparently Obenauf's contains an ingredient that can break down the adhesive and cause delamination of the rubber rand. That's why there is that note in your Kenetrek box that advises against using Obenauf's. The Kenetrek boot wax is very similar to Obenauf's Heavy Duty LP and it does just as good of a job for protecting and waterproofing leather. That being said, I used Obenauf's Heavy Duty LP on a pair of Danner Mountain Assault's without experiencing any delamination of the rubber rand. I was careful not to apply it directly to the seam between the rand and the leather boot. If I do get any delamination I'm fine with using shoe goo to fix it.
For any boots that are bonded with adhesive (like the rubber rand on your Lowa's or Kenetrek's) I go with the Kenetrek boot wax. Apparently Obenauf's contains an ingredient that can break down the adhesive and cause delamination of the rubber rand. That's why there is that note in your Kenetrek box that advises against using Obenauf's. The Kenetrek boot wax is very similar to Obenauf's Heavy Duty LP and it does just as good of a job for protecting and waterproofing leather. That being said, I used Obenauf's Heavy Duty LP on a pair of Danner Mountain Assault's without experiencing any delamination of the rubber rand. I was careful not to apply it directly to the seam between the rand and the leather boot. If I do get any delamination I'm fine with using shoe goo to fix it.