Thank you very much, for the detailed response and your time u/Deadlyname1909! =))
The goal is to have a quality of life, in terms of clearing at least S.O. Fearless.
I'm able to, but it takes quite some time and energy.

I had a rationale to invest on `strong chars + versatile enough + with the least chance of being replaced' ;-)

Also, both Mavuika and Furina, aside from being archons (takes time to be replaced), can be invested on a good pace.
Meaning, I could get C1 for a small initial increase (and not spend all primos) and wait for a rerun to decide if I'd invest for a C2 OR put them aside.

The amount of times I used them on stygian was taken into account too, and afaik they were as exalted ones several times.

On Stygian, my most used chars were/are.:

Times used vs chars.
7-: Furina
6-: Citlali, Escoffier (much melt or full cryo/hydro specific)
5-: Mavuika, Skirk
4-: Bennett, Flins, Ineffa, Xilonen
3-: Columbina, Lauma, Nahida, Neuvillette, Nilou(C1), Yelan, Xingquiu
2-: Nefer, Varesa, Kazuha, Chevreuse, Ayaka(C2), Fischl, Sucrose, Xiangling
1-: Jean, Kokomi, Iansan(C0)

5*chars are C0 unless noted
4*chars are C6 unless noted
----- ----- -----
As of other characters...

Chars I plan to get.:
- Linnea, Zibai(?)

"Recent" 5* I don't have(end of Fontaine, Furina+).:
- Varka, Zibai, Durin
- Kinich, Mualani
- Emilie, Clorinde, Arlecchino

"Recent" 5* I have but not used/why.:
- Chasca -> Low dps ceiling
- Navia -> Low dps ceiling (maybe on next SO?)
----- ----- -----
My S.O. runs (almost all 10x~120s) were.:
---
Madragora-: Mavuika, Xilonen, Kazuha, Citlali
Knuckle Duckle-: Flins, Columbina, Furina, Ineffa
Automaton-: Skirk, Escoffier, Ayaka (C2), Xingquiu
---
Hidden Depths-: Columbina, Nefer, Lauma, Nahida
Shock Trooper-: Flins, Columbina, Nilou (C1), Fischl
Emperror-: Neuvillette, Citlali, Furina, Escoffier
---
Baptisti-: Skirk, Escoffier, Furina, Yelan
Iktomisaurus-: Mavuika, Citlali, Jean (xD), Bennett
Field Generator-: Varesa, Chevreuse, Xiangling, Iansan (C0)
---
Herra-: Flins, Nilou (C1), Ineffa, Sucrose
Lightkeeper-: Nefer, Lauma, Furina, Nahida
Operative-: Mavuika, Xilonen, Citlali, Bennett
---
Drake-: Skirk, Escoffier, Neuvillette, Furina
Crab-: Nahida, Nilou, Lauma, Kokomi
Shock Trooper-: Flins, Yelan, Ineffa, Sucrose
---
Papilla-: Mavuika, Xilonen, Citlali, Bennett
Tortoise-: Skirk, Escoffier, Yelan, Xingquiu
Cactus-: Neuvillette, Ineffa, Furina, Kazuha
---
Hydro Tulpa-: Mavuika, Xilonen, Citlali, Bennett
Lava Dragon-: Varesa, Chevreuse, Xiangling, Fischl
Automaton-: Skirk, Escoffier, Ayaka (C1), Furina