I've tried most emulators. LDPlayer, Bluestacks, Nox, Memu, Mumu. From time to time, for some reason the game will limit its FPS to 30 for no reason. Opening ingame settings will fix the FPS back to 50-60. Then it will repeat again. This happens in all emulator that I tried. Seems to be a problem on the game itself. Out of all of them, LDPlayer works best for me. 50-60 FPS
EDIT: Due to this, I've set lower RAM on LDPlayer because higher RAM doesn't seems to alleviate the problem. HOWEVER, now I tried changing back to higher RAM and the 30FPS frame drop no longer happens. I guess the recent update fixed it?