Sonny Landreth is known for using a variety of tunings. The tuning he will choose (either low or high in tonality) will usually depend on his vocal range. Some tunings require the strings to be tuned UP therefore raising the tonality, others tuned DOWN to lower the tonality. For instrumental songs, tunings can be chosen depending on the tonality desired as they all offer different sounds.

For the first clip “Hell at Home” Sonny is tuned to an Open-A tuning:

low to high E A E A C# E

For the second solo backstage clip he is using an Open-E tuning:

low to high E B E G# B E

Sonny also uses these other tunings which are very accommodating to slide playing:

Open-G D G D G B D

Open-D D A D F# A D

All of the above tunings are commonly used for playing slide guitar.
Hope this helps!

Cheers
Chris Finch