Before you complete level 30, there will be a lot of unknown kanji in anything you read, no matter what order WaniKani presents them. WaniKani aims to teach simpler kanji first. I don’t think there would be much to gain teaching more common kanji at (for example) level 5 versus level 20, but there’s a bit to lose if more complex kanji show up early (making the earlier levels more difficult).
I highly recommend anyone who is starting WaniKani, but hasn’t started reading yet, to start their reading journey with easier material containing furigana, such as the various books/comics we’ve read in the Absolute Beginner Book Club.
Learning basic grammar and then starting reading will help you build the pattern recognition necessary to really get to know the kanji WaniKani teaches and basic vocabulary regardless of whether WaniKani includes it or not.
I think the context sentences are meant to give a better example of the vocabulary word’s usage/nuance, which the English translation helps with even if you don’t know all the Japanese words. Later levels have various words that seem to have the same meaning, but the context sentences show their differences, even if you’re only reading the English translations.