Hi my friend,
Then QualityScaler and RealScaler are pretty much the same, but QualityScaler has support for more AI and is updated more often.
Initially (about 3 years ago) I created 2 different projects because the individual apps weighed a lot and I had a lot of difficulty encapsulating all the AIs in one project. As I progressed, however, I was able to make the apps much smaller, so splitting was no longer necessary, but since I had already put both apps up for sale I decided to make QualityScaler the main app and RealScaler the secondary app but still support both out of respect for those who had purchased both.
I was also a fan of FlowFrameshaha, but just because it didn't update the app anymore I decided to make my own, constantly updated with different improvements.
If you are interested in a FlowFrames alternative, there is my FluidFrames app (https://jangystudio.itch.io/fluidframesrife)