Ranged Upgrade

Are you asking which one to promote? If that is the case Cecilia because she can counter Reinhardt and Brave Lyn and you can merge her to 5*+10 if you want due to her availability.

Would help to know what IV's each unit have. Though, I am leaning towards Tailtiu or Cecilia.

Cecilia is always a popular choice, however she's so easy to get that it might be worth getting her to 4* +10, since her stats will be higher than a regular 5* and it costs a lot less feathers.

I upgraded Clarisse when I first got her cause I liked her design, but I grew to regret that as she is probably one of the worst units in my 5* roster - would heavily recommend against it. I also promoted Ursula recently, however she is actually very good. I find GHB units good candidates to promote as you can't merge them and they often come with good skills. In Ursula's case, an upgraded/refined Keen Gronnwolf is actually super helpful for a lot of the meta.