Hi alavio,
These are placed inside individual coils on the outside edges (or in some cases in various zones inside the mattress) and are an effective method of providing edge support that doesn’t remove the steel and replace it with polyfoam and would be stronger and more durable than the more typical polyfoam surround IMO.
I don’t know the specifics of the rest of the layers (listed from the top down or bottom up) so I can’t really make any meaningful comments about the mattresses as a whole or how they may compare unless you can list all the specifics but this type of edge support is a durable design.
I do think highly of Alex and the Good Bed Guys in general and you can see some comments about them in posts #6 and #7 here.
Phoenix