We have a massive 240v/70a EVSE (~17kW or ~60 mph) in our driveway as well, on the other end of the spectrum as several NEMA 14-50 outlets sharing a 50 amp breaker in our garage.
Clearly, we can't charge at more than 40 amps total with the 50 amp breaker, but I do often plug in 2 cars that share that breaker.
I generally set both to charge at 15 amps (~3.6kW or ~12 mph), leaving 10 amps for garage door opener, lights, etc.
If we arrive late with low charge and have to go somewhere in the morning, I'll only plug one car in and charge at the full 30 amps available or use the 17 kW outside to charge at whatever the car is able to draw.
This is almost always enough for both EVs to charge during our off-peak rates from 10:00 pm to 8:00 am.
I have spent extended time in places where all I had was a NEMA 5-20 and can say that 120v/12a is doable but often inconvenient, especially on those days when I arrive late from work and have an errand like a Dr. appt in the morning before work.
Therefore, I can, from experience, say that 240v/15 amps is enough for our normal driving. 6 kW and above are, on rare occasion, useful but probably not necessary. 120v will result in inconvenience if that is all you have, but, with a nearby DCFC to supplement occasionally, it will probably work as well.
I have up to a 38 mile commute (each way) and can charge at work for what it is worth.
