How much bandwidth will I need?

Moving back into a home after a renovation. Had, and will be going back to Cox internet and DirecTV. Was paying $60/month for 100mbps. Never had a problem with me, the wife, and one child, streaming kids shows on netflix, playing xbox online, streaming music to a networked receiver, downloading large data files for work, etc. Never had any buffering problems or lag in gaming, or anything. Was actually hitting 125-135 mbps at times hardwired to my laptop.

Now, going to have pretty much the same usage, but adding 3 outdoor ip cameras, and a couple more tvs that may or may not have streaming devices on them. Also, going to be adding a couple wireless thermostats, a door lock, and some window sensors. The most that would ever be happening at one time would be streaming netflix, playing xbox, and streaming like HBO Now on a third TV (guessing these are the 3 most bandwidth intensive things an individual could be doing?). The cameras will be hardwired, using POE, but the actual storage is happening on SD cards in the cameras, and the network is just used for remotely accessing the stored/live video. Might possibly be adding Sonos in the future, but I think that runs it's own wireless network and doesn't really use internet bandwidth?

I guess I'm wondering if I can drop down to 50 mbps, or if I was using or may be using in the future, anywhere near 50 mbps. I have an assus surfboard docsis 3.0 and an apple airport extreme (AC), both of which will be located in the center of my home. Receiver, xbox one, and up to 5 apple tvs will be hardwired, along with the 3 ip cameras.