We run three primary tablets for testing the Apple version. The primary one is an iPad Pro with 32GB. The second is an iPad Air2 with 16GB. The third is an iPad Air with 32GB, which is the recommended minimum to enjoy an optimal experience.
iPad minis of any version are not recommended for usability, due to the small format.
Due to the price that iPad Air tablets becoming extremely reasonable, we have ceased testing on older versions of hardware.