Fingerpicking technique question

So I've been branching out from strumming over the past few months to chord melodies and a bit of fingerpicking. I've got Mark Nelson's book to guide me on the latter. So far, I've been concentrating on Twinkle Twinkle (the second "more complex" arrangement) and an arrangement he did of Brother John that I found on Ukulele Tonya. Having loads of fun with it.

Finally popped in the CD that came with the book and was surprised to hear on the chords where all four strings are played Mark strums them and I've been plucking all four simultaneously. A bit of a different sound and I guess either is OK(?). My question is does one just decide which sounds best by trial and error? Seems a bit like playing the double bass and the music not indicating whether to bow or pluck. The TAB notation used in Ukulele for Dummies uses a squiggly line with an arrow to indicate strum down or up, so given no arrow, I assumed plucking all four was called for.

Just thought I'd check with those who are much further along the path than me. Thanks.

I think people from a pop music background generally, or at least often, don't use strum arrows. You can usually tell cos someone who uses arrows probably uses a lot of other articulation: crescendos, staccatos, etc. If you are from a notation background, you might think of it like Baroque music. Traditionally, that had almost no articulation, and a lot of improvised embellishment added by the player. If it happens more than once, try it one way the first time, and another way the next.

If you want an "in between" sound, you can do a roll on all four strings. Put your fingers like you're going to pluck all four, then pluck them very quickly thumb-index-middle-ring. That way, you have a third sound you can use with all 4 strings.