How to Use Mobile Phones to Multicam Livestream for Free! No capture card needed - low cost option

Here's my comprehensive overview of how you can bring multicam into your livestream for free using mobile phones, OBS on your PC and two mobile apps.
I used IP Webcam to connect a couple of phones to OBS via wifi and iV Cam to connect a third directly to the PC and OBS by USB. I'll walk through what I learnt about the pros and cons of each as well as a few things to watch out for.
I was particularly impressed by iV Cam and chose to buy the licence which means I now can use my Google Pixel phone as a good quality webcam very easily.