I do not know the rating on the switches. That is why I bought 10 of them. But the circuit sets the small coil in the starter relay, not alot of current - it does not carry the starting motor current.
One of the problems with dealing with China is getting specifications and drawings on components. So if they are real cheap, you gamble a few dollars that they will suffice.
Yes the switch connects the relay to ground which makes the circuit to energise the relay's coil