Choosing a constant withdrawal percentage (like 4%) is no worse than guessing at a constant rate of return or inflation rate when planning for retirement. Most retirement calculators do that. VPW is, I guess aimed at those who have or are about to reach retirement. Has some merit, but may be too complex for many.
I use CSWR (Common Sense Withdrawal Rate). Just spend what you can afford If you overspend one year, spend less the next year. Keeping average at somewhere in 3.5-4% range seems to work and is simple enough, It is what I use to "control" household spending (no new kitchen this year if we put new roof on last year )