The self leveling will spread out somewhat from the bead that you apply from the tube. If you put a dab on a horizontal surface say the size of a dime, it will level out (flatten) to about the size of a quarter. This is so that when you apply it to a roof seam, it will spread out a s it settles and provide overlap coverage.
Lap sealant (non leveling) does not have the leveling agent and maintains the form of the bead that is applied from the tube. I have used non leveling on the roof when it was all I had and wanted tondona little touch up.
Steve
Steve Rinker
Rochester, NY
2013 Keystone Sydney 340FBH 5th Wheel, 12,280 lbs loaded (scale)
2015.5 GMC Sierra Denali 3500, SRW, Duramax, CC, Payload 3,700 (sticker- not scaled yet)
Take my posts for what they are, opinions based on my own experiences.