I think a few scenes draw parallels to WWWSK,
like the leads being associated with each other for so long, FL saving up her earnings to go on a big holiday, ML behaving in a similar fashion & SML being a jerk etc.,

In both Fake Princess and Alchemy of Souls, both the FLs work for High ranking families( in Fake Princess, for Crown Prince in Alchemy for Royal family Mages)
Similarities:-
1. Female leads are replacements to the original characters
2. Both come from a village backdrop/ country
3. Both possess fighting skills( In Fake Princess FL being a Mountain Bandit & in Alchemy FL being a Trained Assasin)
4. FLs are smarter than MLs
5.Both FLs have birth secrets
6.Both involve the FLs hiding their secret identity

Differences:-
1.Alchemy is more about magical, mystical elements (like WUXIA) while Fake Princess is a light hearted Rom-Com
2. AoS has a second ML( major SLS alert) unlike Fake Princess
3. In Fake princess, ML fights his brother for the throne unlike AoS