We are Verizon customers who went to eastern Canada in 2016 and western Canada in 2018. Verizon offered a $25 per month plan for talk and text only, or a $5 per day "travel pass" for talk, text and data. The $5 per day is charged for every day the phone is switched on in Canada. We put my flip phone on the monthly plan, and my wife's smart phone on the travel pass.
Interesting result: The monthly plan linked to Rogers Cellular in Canada, and the Travel Pass linked to Telus in Canada. Rogers Cellular had little coverage in out of the way places, while Telus had much better coverage. Thus my wife had reception in a number of places where I had no service. In the US, both phones had service in the same places.
By the way, we contacted Verizon tech support to try to get my phone working, or to at least get my calls forwarded to the working phone. They seemed unaware that there were different Canadian partners, and pretty much blamed the phone itself for the problem. Once we got to a large city reception returned.