@debbie_o You’ll need hands-free in the car. If the car can’t provide that, a connect clip will.
As to a used iphone, it is the way I went two years ago getting a 5S. The S series are newer hardware than the 5. This holds true for all S models and they get updates a year more than their standard counterpart.
The X is a really new idea with facial recognition instead of the fingerprint button and the X is button-less. There are complaints in reviews as it is something some people don’t care for. If you are going to iphone from android, it probably won’t be as annoying. So a used 7S would give you a comparable phone to the new 8’s and a long term upgrade path with IOS.
So, it is something to consider.