Questions incoming ! Yeah ! (or not...)

[Kyanon]

Hello everyone ! I don't post that much but I read this forum quite a lot, so thanks for the help you usually bring to me but right now I'm needing a little more help ^^'
As usual, please forgive the mistakes you'll find in my posts, french baguettes don't speak english very well (omelette du fromage, yes...).

1) I'm now into a point where I don't really know which units I should upgrade (by levelling, CCing or awakening them). I think I begin to have an interesting core of units, but with the recent rush of events I don't have that much time to build them and I don't really know if some niche units are really interesting to use (looking at you, Flamel). I was planning to 50CC60 Zola first, then Yuyu second, but then, I'm at a loss...

2) I took a look at the upcoming events (YoxalLoyal, may the God of Waifus bless you for this good action...), and I saw 2 collection events beeing listed, one for a black ninja and the other for a platinium Priestess Warrior. Since I already got Saki and Flamel, is there any interest for me to farm a lot and spend SC to perfect the units from those events, or should I keep my SC since I got some replacement for those two ?

3) Flamel. I initially though of her as "AW her, bring her to level 90 and nine times out of ten you'll never use Leeanne again", but on a second tought I would spend a shitload of ressources for her... Is she really worth it, or is she too much of a niche unit to invest on her ? And has she some use out of the classic "healer on a melee slot" ?

Sorry for taking your time on those interrogations, and thanks a lot for those who will bring me any useful comment