@ownwonnow I use and have used Mobile WiFi (or hotspot or MyFi) and It works fine if you are in an area with decent radio data connections (4G/5G).
I presume you have used your phone as the device (that converts mobile data into WiFi). This has the benefit that you can share the airtime contract between your norma phone use and the WiFi. It has the disadvantage that if you go away with your phone the WiFi goes with you. Anyone back at base expecting a WiFi service will be disappointed.
You can buy small devices that do the interfacing separately from your phone, but you then need a new SIM and airtime contract. I have used this in an office (was in a 5G area) where several people shared the WiFi. It worked pretty well (not quite as good as a decent fiber connection).
Security seems reasonable - but if you are concerned you really need to set up a VPN whatever type of service you use.
You may want to get an "unlimited data" airtime contract (else you run out of data pretty quickly). You then run into endless small print restrictions. I think all providers allow you to use hotspots (they used to be excluded). but I have had one who despite giving me unlimited data, restricted the "shared" data.
You can get "data only" SIMs. whats the point of free phone calls into a device with no phone.
