The only purpose of a breaker is to prevent current from heating up wires beyond a safe level. They don't indicate anything about power capacity for a given neighborhood.
However when you sign up for Services you sign up for a given Amp level of service, the Power company then has the expectation to be able to supply you with that level of current at that location
Most residential Homes have either 100 or 200amp service. 100amp service would probably be enough to run about 50 cards (assuming each card running at at 250w power draw that may be high no idea)
> In one instance last year, the transformer outside a bootleg miner’s home overheated and touched off a grass fire, Chelan County PUD officials say.
If a transformer is rated to supply 1000A then you should not under any circumstances allow more to be drawn from it.