the speed shouldn’t be much different by doing radicals only compared to doing radicals+kanji (and anyway you’d need to enter the correct answer for the kanji to unlock levels anyways).
so if anything, i’d leave out vocabulary and only learn radicals+kanji.
But i would advise against that, because the vocab really helps remembering the kanji.
also, a lot of the vocab is useful, also for the JLPT.
i’d simply use reorder and ignore on the level-critical radicals and kanji, and go fast that way. You can stop using ignore when you’ve guru’d kanji and radicals. One and a half years is plenty to finish WK that way.
i’m doing vocab and going at 7 days a level, which means i need to do about 200-300 reviews a day at my level (it takes a while for master+ reviews to pile up).
if you go for around 9 days per level, which would be around 1.5 years, it’ll be less.
i do need 1-3 hours per day. (~1.5 hours without lessons, ~3 hours with lessons)