I lowkey think the Tsaritsa is an Ana Schariac expy and the third decender is a Chen Tianwu expy. It makes sense narrativly as well (especially with the expies of herrschers in genshin following similar themes and every expy of a herrscher is an archon or god) Ana and Chen Tianwu were a story about love and how that love couldn't save them (ana herrscher of ice, Chen Tianwu herrscher of the stars... Archon of cryo, decender from the stars) Chen Tianwu doing everything to save ana and turning against his friends, the world, humanity to save her murging himself with her to give her a chance, now Ana (Anastasia) doing the same, doing everything for that love, turning her back on her Nation, on her very concept of God hood, on the very laws of her world... For vengeance, for love for the chance to have him again (if the theory she wants to bring the third defender back to life is true)
More on the third decender being brought back latest archon quest has revealed dottore has figured out how to put souls into bodies and dottore also knows how to make bodies (segments) and the gnosis being the actual body of the third decender...
Also Tsaritsa can't be a bronya expy as we have seen her outline and she doesn't have the massive ringlets that all bronya forms and expies have (captain verse and hsr confirming this) and Bronya has Seele as her lover (thank you manga before hoyo was made to retcon it cause of censorship) while third decender is male.
Wendy is all about regaining her freedom and anatomy but she is killed before she does (Venti is a Wendy expy and is God if freedom) Welt is tied down by promises he made to others, and himself and how they trap him (contracts) there is also ith of them being pillers (Welt through being the only herrscher at the time to side with humanity and so he had a duty to save humanity, Zhongli with being the Archon of Liyue and creating money, both pillers) and both entering retirement but willing to exit it when they are needed (Welt has already left retirement) and being the oldest of their group (Welt oldest herrscher and Zhongli oldest Archon). Raiden mei is all about doing everything for one person and learning to extend that to everyone else and feeling lost without Kiana as her motivation (ei and Makoto doing everything for each other and Makoto dying leaving Ei stuck and unable to move on, finding that motivation to be part of the world again) Himeko (I believe Pyro archon is himeko from previous era expy instead of Murata himeko) being pure destruction (the divine key made from her core is the most destructive) being chosen as a herrscher because of her efforts to try and save her world while Mavuika using that destructive fire to save her Nation to destroy and cleanse the corrutive force of the abyss (with pe himeko being consumed instead) and pe himeko not leaning on anyone and being alone while Mavuika learns to relay on others (traveller and the special warriors (forgot what they are called very sick atm)) Nahida and Furina and Foculas aren't expies of hi3 characters so I won't include them. But yeah these are my surface level thoughts on hi3 and genshin herrscher expies.