on another floor, a fair distance, yes it is 5Ghz
The speed and latency deteriorates very quickly the further and further you get.
Another floor is fine where you're still relatively close to the router, but when you're going through multiple walls your speed starts tanking.
It's upto OP to decide whether 5Ghz would be suitable for the distance he is covering, if it is not, we're only talking about 2.4Ghz.
And by no means should you expect stable latency with 2.4Ghz & and definitely not the throughput that he'd expect.