The second one is charging hourly. We tend to prefer hourly fees on projects that are particularly open ended or very small scope. Our hourly rates are currently between $60 and $120 per hour depending on who is doing the work.
The word sonder exists, though. It means to probe, and in a more specific use, to test the depth of something. The word sound (as in the water feature) is a cognate, both related to the Old English sund meaning to swim, or the sea. I can't really think of an English equivalent that's specific beyond mere awareness.
A meander is a bend in the river, it is usually in the lower and middle course of the river where the water slides from one side of the river to the next, this erodes one side of the river bed and deposites sediment on the other to make a bend. This bend gets bigger as the process happens again and again.