I have a giffgaff e-sim which is connected all the time in Thailand. I only use it to receive OTP's,etc. from the UK and when I have to go there, hopefully never. You can keep multiple e-sims on your phone and switch them on and off as needed, i do this when travelling. And yes you can use as a hotspot. My physical True SIM just stays in the phone and data is turned off when travelling.