S24 has poor battery life most likely due to exynos. Could get the s25 if possible.Pixel 9 also not good because of Tensor is not good processor as of yet.
It's good to hear that Watch 4 will get the OneUI 8 update (source:Sammobile) but if the previous OneUI 6 update is to be believed, OneUI 8 is going to take a year to arrive on the Watch 4.
Do a software initialization then. The option name might be either "software initialization" or "emergency software". Something similar to these. Note that this will factory reset your phone and smart switch will download about 3-4GB of the software ...