From what I can tell race foilers have two primary modes of going off the wind. In high winds, they load up and point downwind going faster and faster allowing them to point lower and lower. This feels practically suicidal for beginners like me! When the wind is light, they sin and loop the kite continuously which allows an even deeper angle of direction with less boat speed. The foil kites require some tension in the lines to maintain shape, and the ability to respond and recover.
The drift discussion as I can relate to it, is about traveling deep off the wind, but not necessarily in a real hurry. You can park a strut less LEI without needing to work it and just keep heading deeper and deeper off the wind at nice controlled speeds. The kite won't deform or misbehave and any falter is recoverable with a quick turn away from the kite.
If the foil itself opens up 45 degrees of direction on the upwind side of the compass, kites like the cloud open up another 45+ degrees on the downwind side. In truth any kite will allow you to head deep off the wind, it's just being able to do it without having to work the kite, always being mindful of when the power is going to kick in. Its another level of tricky when the strut of your foil is vertical and you are not loading up the foil to lean against. Most times heading off the wind, I have very little tension in the lines and I am more or less upright on the foil. Small continuous turns help maintain some feel to balance against, but you can do it straight line too. It feels very precarious and I really appreciate not having to divert any attention to the kite. There is a really nice nose rider sensation to going downwind with a parked LEI where the kite is nearly out of the equation altogether.
Riding a foil with the strut at 45 degrees feels much more stable (read, heading across or upwind). You use the strut to help control depth and to balance against. When riding very upright (read downwind) you are only using the wings for depth control and it much more a fore and aft shift to keep it all together. You are truly balancing instead of leaning against a balancing pressure.