In terms of their armor performance, Angel Armor is listed on the NIJ Compliant Products List so I wouldn't be concerned about the stated performance.
Not sure how realistic the concept is to be snapping and unsnapping armor for varying threats but I see nothing wrong with it so long as the two halves do not separate/shift when hit and if the areas with the magnets provide the same ballistic protection as the rest of the plate.
If you don't see yourself using the modular feature, I'd probably just go with a standard special threat plate or a LW level 3/3+ as you can probably get lighter and thinner.
Aside from that, I don't have much else to add. I did hear they're part of a larger company based overseas... Blue Ocean Group?