Phone recommendation for FGO?

Hmm the website's requirement for Android

A Smartphones or tablets with Android 4.1 or higher and 2GB or more RAM. (Incompatible with Intel CPUs.)

*It is possible that the game will not work on some devices, even with the recommended version or higher.
*Incompatible with N-08D, SH-06D.
*Incompatible with beta versions of OSes.

In other words, they all pretty much work. Just pick your favorite. For reference, I'm using a cheapo xiaomi note 5 and OnePlus 5. Both work equally well.

I use S9 Plus (Exynos) and playing FGO on it is not as responsive and smooth as S9 (Snapdragon) and LG G7. However, this was remedied by flashing a custom kernel from XDA forum.

So if you don't mind modifying the device, tripping Knox and voiding warranty, then S9 Exynos might be for you.

Otherwise, if you prefer to use the device normally, then I recommend LG G7.

P.S. FGO is more performance optimised for iOS devices so most iPhones and iPads will run this game smoother and more consistent than Android devices.

I picked up an S9+ earlier this summer (coming from a Galaxy Note 5) and let me tell you the improvement was very noticeable. The game runs almost completely smooth for me now with the rare exception of some delay with swapping in servants or after a servant dies and another replaces it, though to be fair I've seen this on other people's devices and even recordings of gameplay so it might just be the app itself.

I had lots of lag before with heavy effect NPs like JAlter or LArtoria for instance but with the S9+ it's all completely smooth. Now, I didn't buy the phone just for FGO, but if you're already looking to upgrade your device I'd totally recommend that one from personal experience.

Oh I guess I should mention I'm using the US release which I guess is the snapdragon. I didn't know there were different versions.

I use s7 edge with exynos... the only noticeable problem is lag when switching servant or when you use a new np animation you haven't used before... (it didn't happen when you clear cache.. so completely happened only on a new servant that you haven't use before)