It's been suggested before, but buy plates first then choose a carrier.
As for determining your probable threats - what calibers is your department seizing in the field or not?
If a specific caliber &/or load isn't listed, identified then it probably was not officially tested. Now that doesn't mean no one has shot that round at that plate just that it wasn't done officially.
Have you reached out to a competent Hesco dealer, run your situation & needs past them, and gotten their recommendation? More than once over the years, I've gotten on the phone with reps from US Armor, Point Blank, Armored Mobility, and AT Armor.