i always do a lot of ahead-planning with chanters, because it's easy to go "bad" on the chants IMO. if you have too many it's hard to make good use of them all. chant mechanics are also significantly different from poe1, just as a reminder. (everything is a flat 6s on, 3s linger [except for troubadour stuff], whereas in poe1 it varied based on character level and chant level)
to your questions: i love all the resistance chants. in order of usefulness, i would go "one dozen" (resolve/con resistance), "fampyr's gaze" (int/perception resistance), and then "hit the deck" (might/dex). one dozen because i always do megabosses so a chanter is an easy way to fight auranic, plus i find frightened and sickened/weakened awful common for how annoying they are. int/perception because charm/dominate is super annoying in fights where it has, and perception resistance is super useful especially in fights where enemies have persistent distraction.
because they're so niche, it helps avoid the "too many chants" problem because i create one or two songs that just focus on the resistance chants and switch to them only if needed.
i always start with the one dozen chant in any "resistance" song, because especially when sickened/weakened/enfeebled kick in i want to dispel it asap so i can heal.
literally every chanter i ever have these days (and in like the past 500-600 hours of gameplay) picks up one dozen, that's how much i love having it around. really punches above its weight for being just a tier-two chant.
i used to love thick grew their tongue a lot in the earlier days, but i have a lot more ways to deal with concentration and am more deliberate about interrupts so it's a little bit less important.
everything else is more situational on what my party/chanter are like and what my design goal is. i'd say ancient memory is a pretty safe choice for all setups because of its great utility. sometimes ordering can help, especially when you consider that when you use an invocation or you switch songs you immediately jump back to your first chant, so effects that can double up or benefit from being refreshed faster or are offensive and need attack rolls so having multiple checks are good. like the skeleton summoning chant, or the damage shield chant, or the anti-concentration chant. it might not sounds like it comes up a lot, but in practice with the most obvious indication (the skeleton summoning chant) i would end up with a lot of extra skeletons just from having it as the first song. there are also a couple minor synergies, like having mercy mercy (+50% heal) or one dozen before an ancient memory chant, to boost the healing effectiveness.
in general though i would argue against having more than three songs in a chant. the math changes a bit with a troubadour's better linger (up to four maybe), but typically beyond three you're not really adding more power and you're just adding more variability:
with any choice in a game, there's always a "best" choice, a "second best" choice, etc. when you fill up chants in a song, what you're really doing is selecting a "best" chant, a "second best" chant, etc. after a certain point, each additional chant you add to a song lowers the average quality of that song. ideally you don't exceed two chants in a song, because with proper intellect you have 100% uptime on your two best chants. but in practice i find it a worthwhile to add a third to add a little bit more flexibility (especially if it's adding something like ancient memory where even a little goes a long way) even at the cost of uptime of your other arguably better chants.
this is different than in poe1 where the different chant durations and the reduced active chant time as you level up means there's some interesting math and strategizing about mixing in shorter chants with longer chants that have huge linger.