Help me finalize escape from VZW... what USM plan? Prioritized vs premium???

Hi. I'm not really sure I understand recent posts, but it looks like (maybe) USM plans have changed since I last was working on our escape from VZW.

I have 4 lines. On the "welcome" cheapest tier at VZW. Deprioritized. Pay extra for one of us to hotspot. somewhere in the $145/month range, but who can understand why it goes up and down with VZW.

It looks like USM now has a 17.50/month/line (paid annual) for some kind of "unlimited". That looks like $70/month for 4 lines, at quite a savings. I had previously thought by-the-gig would be best, but it clearly seems not to be? What am I missing? What are the gotchas in the 17.50 plan?

Only 10gb is "premium"? Does anyone know what exactly premium means? I thought I had heard that, if on their version of VZW, your data is *not* deprioritized, or is at a higher level than my current verizon plan. (But not if on the other networks) I'm concerned that they also advertise higher plans as having "priority" data ... I'm confused. Maybe this means that with the higher plan you can be on any network and not get deprioritized?

I *think* our dissatisfaction with our current data stems from depriotization, and that VZW is probably the best coverage in our area. So then it would be "warp" for us?

Anything I should know in preparing for the switchover? Anything else to consider? Last minute case for a different carrier? TIA