I’ve had similar issues with my Galaxy Note20 Ultra. To be honest with my experience it’ll be every time I plug in the charger that it’ll go from 2hrs to 8hrs on charge. It could be just the wire that you use for charging

I say go with your gut with whatever you feel is the best for you. Right now I have a Galaxy Note20 Ultra and I have to admit that even in 2023 the phone is absolutely amazing. It has 12GBs of RAM and a 100MP camera that can make some photos truly stand out. Not to mention a 120hz display that makes movement smooth. The Note20 Ultra still competes with the most recent flagship phones and is quite cheap now☝️