[mananaysiempre]

Lowercase w resets (each) selection to end of selection, skips any whitespace, and selects to next word boundary, so www or 3w will select third word counting from cursor. Uppercase W extends selection over any whitespace and then to next word boundary, so WWW or 3W will select from cursor to third end of word. (Most other movements are also in lowercase resetting / uppercase extending pairs.) Thus with length-1 (that is, initial-state) selection you can do wwwd or 3wd to delete third word and preserve whitespace, wWWd or w2Wd to delete three words but preserve whitespace, WWWd or 3Wd to delete three words and any whitespace between cursor and start of first word.

That is, counts work, it’s the movements that are slightly different. See manual §3.4–6[1].

[1]: https://github.com/mawww/kakoune#34-movement