I am always gratified to turn up BB content that affects intros and walkups, that being an area I have gradually relegated to a kind of rote, as in routine, translated, boring. The walkup is one of those areas easily ignored.
I had the pleasure of working with one of South Carolina's top Southern Rock and Metal lead guitar players, years ago, studio work, me comping keyboards. I recall how he used to stress walkups. Me, learning as much as I could at the time, but never really delving into it, my skill level being as it was and is.
We all know the drill. Amazing Grace in Cmaj for example, picks up a G-note for ("A") and kicks off the first bar of the melody with the root C (" -maz") finishing the first bar (3/4) with tied eighth E and C notes ("-ing") for that familiar two note syllable. What's often looked at is what comes before that pick up G note, which is, of course, a half note C that comes at the end of the chorus, and it sounds like (C half) (G quarter = 'Twas) || (C) grace ....etc...
That is is a little walkup.
My point is that the first words of the verse can be the final notes of the walkup.

Yes, these techniques add what I call 'tension' to the song, especially when they are allowed to resolve.

As an example, it's like playing an F chord in the treble and holding a strong single Bb in the bass. The listener anticipates that it's got somewhere to go, and the resolve finally releases the tension.

That's what I mean. The four is often thought of as the resolver of tension created by the five, or the interplay of the one-three-five, in your example of the F key, is it not?

Video Track is charting, either from playing, memory or in a journal, exactly what my post was getting at; namely, study, analyze, and listen in order to build the framework that can introduce a song, act as a fill between verses, or even within a verse.

Simple 4 bar intro w/ walkup:
(last bar C-D-E ) -----------------la la la
(bar one w/ pickup G) ------------ eye
(second bar A-G) --------------- was raised on
(third bar C-D-E-F)--------------- coun - try sun - shine...
( bar four hold the F) -------------hold / rest / pick up line one

So, that's the general idea of where I am with it.
Also, useful to think of first G note as "landing note"
Pretty elementary for music students, which I ain't.