Because of how iOS multitasking works as well as efficiencies gained with iOS 13 you really don't need a ton of RAM. It'll run just fine with 3 GB and will probably have decent battery life as well.
I've heard that iOS 13 RAM management is quite aggressive compared to the earlier versions of iOS, but I base that only on iOS users' observations.
The thing I'd actually be worried about is the phone's usability going into the future, but then, if it won't be used for too long period of time, that might not be a problem. I'm saying that because the 4GB of RAM that my current phone (Huawei P20) has was all sunshine and roses back in 2018 when the phone was new, but nowadays, I wish they put 6GB in it. And it's not even on Android 10 yet. But again, that might not be the case with iOS so much.
I've heard conflicted rumors on this one. I hope it comes in 5.5" size but I'll get it if it doesn't.
Yup, I've heard those other rumours as well, but I guess we can just wait and see. Perhaps there's a possibility that a larger variant will be released further down the road.
Right now I'd be buying the Galaxy A71, that camera is mighty impressive. Especially considering the cost and the huge screen, I suppose it's a middling phone for everything else.
That thing is not available in the USA yet, and if GSMArena is to be believed, it won't come out in the US until summer.