Heres my opinion from experience on those blades...
The first blade is only good for aluminum and roofing tin and very thin steel.

Those grinder cut off wheels will work but you will need quite a few of them.

Grinder cut of wheels will throw tons of sparks and may catch whatever is inside on fire.

If its its a fire protected safe it will have about a 2 inch layer of some white powder between the layers of the steel. That stuff could be toxic i dont know.

This is all dependent on what kind of safe it is. Is it heavy for its size or light?