I am wiring an old house with new wires and want to have an outlet outside for charging a potential electric car. There is no carport or roof overhang, so weather resistance is important. The wall is still fully open to studs and I have full access to inside and outside of the wall. I was considering a stove or dryer outlet. The house has 100 amp service, but everything inside is on propane, so I would never draw more than 30 amps during normal home use.
Most likely the EV charger will want a NEMA 6-30 or 6-50.
But you can never be sure. It might require a 14-50 or 14-30.
You can certainly preclude any of the NEMA 10 types (hot hot neutral no ground); those will never be used on an EV (except in old homes hijacking the dryer connection).
The "universal donor" cable would be a 6/3 copper. This will allow up to 60A (though, 60A would be hardwired). Some EV chargers are hardwired.
As far as the breaker, they all cost $10 (assuming your panel has space). So you could buy one pre-emptively, but I would just wait.
I certainly hope you picked up on the importance of extra spaces in a panel from countless discussions here and elsewhere. Spaces are dirt cheap at install time; not so cheap later, so I recommend you finish with almost half your spaces unused. Even if that means junking a panel you installed yesterday; believe me, you will thank us later! Although there's nothing wrong with just adding a subpanel; if well-placed it can even cut down on long wire runs, so can pay for itself in wire.
I concur with your assessment that you are unlikely to draw more than 30A much, or to be more precise, I see no trouble with your house supporting a 60A EV charger.
In my humble opinion, I'd run #6-3 w/ground from the panel to a outlet box accessible from the outside and just cover it with a water tight cover. Wait until you get your car and then get the breaker and outlet according to the specs for your car. If you're running conduit, run a 1" conduit from panel to outlet box and pull the wire later on when you know the specs.
Something commonly installed outside with the amperage that you need would be a 50A RV hookup. If you search for what that requires, you'll find weatherproof enclosures and the expectation that everything will be outside and weathertight. If you try to look at how to install a stove or dryer connection, you'll get the wiring right, but might not find the right enclosures, conduit, etc.
I also think that since it is such a common setup that a future charger might even have some sort of adapter to make install easier. Even if not, the 50A outlet can be easily removed to hardwire the charger.
Every socket is generic when you have the right adapter. Yeah, that sounds stupid but it is the way the world works.
Having installed wiring for my Tesla, I can offer a recommendation similar to Harper's. It's unlikely that you will want or need more than 240V X 60 Amps for any car (until you move up to a Level 3 Supercharger -type system, and that's a seriously different cost bracket). So, install a breaker & wiring gauge to handle that much, and hold off on installing the socket or port until you know what you want to use. Tesla, Chargepoint, and others will sell a wall-mount controller with cable; alternatively you could put in a NEMA-XX and get a cable& controller with adapters to match.
In my case, I have the Tesla-supplied cable which sports adapters for 120VAC (20 Amp), NEMA14-50, and at least one other socket. I have found intermediate adapters on Amazon to connect the Tesla cable to sockets designed for laundry dryers, electric stoves, RV camper connections, and so on.