It doesn't have to be an iPhone to work with an iPad. If the phone is capable of setting up a wifi hotspot then then iPad can link to it. The drawback is the phone's battery life is shortened. I have found the wifi only has been sufficient but it depends where you go.
Qualcomm Snapdragon 835 benchmarks: Antutu, Geekbench 4, GFXBench and PCMark results