Nice, I like apps designed for GTK. It's like the app is made for my operating system instead of running through three compatibility layers and a dose magic.
Yes, aarch64 indeed works for ARM. AArch64 is just another name for ARMv8, the architecture that most modern ARM-based processors use. ARMv64 or AArch64 implies a 64-bit architecture, which most modern devices use nowadays. If something is available for AArch64, that means it can be used on devices with ARMv8 (or new) processors.
Choice is good, I guess, although I'm perfectly happy with the official linux and windows clients. Works really well and plays very smoothly on my old laptop and desktop.