Something I really appreciate in ATSV that I hope we'll get more of in BTSV: the quiet moments.
Something I think often gets lost in the praise of these movies is how often they allow themselves to stay in quiet moments where little is happening and it's all just to soak in the moment and atmosphere and feelings of the characters, and/or sometimes to listen to a character monologue for a long time, without it ever getting boring.
I think ATSV especially was great with this with Miles and Gwen's clocktower scene, Rio's speech to Miles, Miles watching Gwen while he's invisible before she leaves, and Miguel explaining Canon Events. Especially when many other animated movies today seem to have this notion that "something must always be happening or moving" so that 'kids won't get bored' and there can be few moments where they just let the movie breathe and let a moment and atmosphere sink properly in before very suddenly jumping back into action or 'noise' again. Even when other animated movies do it, it's often reserved for one emotional climactic moment, not done several times throughout the movie. ATSV, again, has at least four of these very long quiet and atmospheric moments.
I think that also speaks to how 'brave' the Spiderverse movies are, it can be a gamble to include long, quiet moments like this in an animated movie after all (or again, a character talking for a long time), because yes, you risk the audience, mainly kids, being 'bored' with it, or calling it an 'unnecessary' or 'filler' scene. And yes, I do remember there were viewers of ATSV who said they thought Miles had 'too many scenes with his parents', or generally calling the film 'too long' and that it 'could have cut down on filler'. These aren't opinions I have seen often, however, so I want to assume they remain in the minority. I personally don't see any 'filler' scenes that ATSV could have removed and not have it hurt the film in some way. (If you do think so, however, I'm open for the discussion.)
All this is to say I really hope these quiet and atmospheric scenes are something we'll get in BTSV too and that the trilogy's finale doesn't fall victim to the "something must always be happening" pattern that other animated movies (hell, even some live-action movies, particularly superhero ones) can fall into today. I expect that similarly to ATSV, we'll get more scenes like this with Miles and Gwen, and Miles with his parents. Perhaps there'll also be a quiet scene with the two Miles talking about their different (and yet still similar) lives, a scene with Miles and Peter B reconciling etc. there are many possibilities for it and as long as the writing of them remains as strong as they've been I personally welcome all of them.
Tl; dr: The Spiderverse movies and ATSV especially do a great job of adding long and quiet moments that are either pure atmosphere or characters monologuing without it ever getting boring and that's something they deserve praise for as much as the action and animation I think, and I really hope we'll get more of them in BTSV.