Yeah the last one was easier. I didnt farm the event at all, only the last 3 days of the event (I messed up honestly. Could have done that but was trying to run story missions for big EXP to get a decent level and Stamina pool going) and still got enough to turn her into a rainbow. Though admittedly 2 copies of her dropped from the 10pull gacha as well so that helped as well. At one point I got lucky and got a tripple drop of the girl, which helped a lot.

Got all 3 of these. They are good to have. Especially since the Archer class seems to be lacking in numbers so we have to do with whatever is at hand.
The last one, the "bomb shell with magic clothes that defy the laws of gravity" is one I wanted back in the day of original GS, fairly happy I got her now
The promoted 3* archer is a solid one and easy to evolve just like you said. Got mine on L81, slowly pushing her upwards whenever I got enough dupes for another lvl unlock.
So far no luck on the Tower maps either. Keep running the first one that has worse coin drops but has a chance at dropping the Speed enhancing trumpet. After the one you get for first time clearing the tower, all I got were coins (which again, the second tower drops more off), so no luck there either.