Balance one core question

After many years of service, our CISCO RV 320 has seen better days & will be replaced in our father & son business.
Based on my experience in using the MAX Transit CAT 18 in my RV, my son purchased one to be used when he travels in his RV. We have both been very impressed with the CAT 18 cellular router/modem & the Pepwave products in general. And, the the CISCO RV 320 bit the dust.
We are considering purchasing a Balance One Core device as the primary router for his home office & want to use the CAT 18 as a fail over in the event his cable internet (happens frequently) is lost. We also want the flexibility to simply unplug the CAT 18 from the network and use it when he travels in his RV. The home office network has a multitude of wired & wireless devices. While traveling, he will also need to access the home network.
OK, some questions:
In reading the manual for Balance One Core, I believe it stated you could tether an Android phone via it’s USB port. No mention is made of Apple phones. Does this mean they won’t work period, or, will only work at a greatly diminished fashion?
My assumption is the CAT 18 could be connected to one of the 2 WAN ports, & the Balance One has enough built in intelligence to switch over to the CAT 18 if/when the cable internet fails. Not withstanding some configuration changes on the Balance One.
In addition, I assume if I simply unplug the CAT 18 from one of the WAN ports on the Balance One, it would be the equivalent of never having it plugged in to begin with.
As a side benefit, I assume the UI on both products would be very similar which to my way of thinking is a bonus.
Conceptually, is this a viable solution so as to not have to deal with all the devices, wired & wireless, he has installed in his home & office?

Apple tethering doesn’t work.

A Safe assumption.

Yes,

Slightly different but very similar. Check out the balance demo here http://balancedemo.peplink.com/ (admin/admin)

Conceptually - a balance one that can failover to a transit when you have a primary internet connection outage makes a lot of sense. That is the whole point of the newer Balance 20X which has an inbuilt LTE modem - so what you’re planning to do is ‘normal’ in Peplinks world.

Thank you for your response. Very helpful & informative.