I think you'll find that the majority of those countries are 100% "on certain days." Meaning that they still need to be supported by natural gas plants at the renewable site, or by nearby countries who do not have 100% renewable.
Hydro power is the most efficient way of storing the extra energy right now. So people talking about batteries would be talking on a much smaller scale, or don't know what they are talking about.
A large portion of the energy currently consumed is by oil tankers that burn crude directly during transport of goods across the ocean. The benefit is for transportation of the energy and fueling costs. I suspect that we will need to make energy so cheap on land and for cities that it is more cost effective to create burnable fuel for ships than to extract the oil from the ground.
We are currently struggling to get our cities even at parity with renewable, but maybe with the surplus renewable energy on good days, we could convert that energy to some kind of liquid fuel that could eventually be used on these tanker ships and in planes.
The only counter argument that I've seen that seems to make any sense is that we could use up too many resources trying to reach parity with the current energy consumption. Think like we run out of neodymium for all of the electric engines for both our cars and wind turbines, or run out of materials that go into making all of the solar panels. If that's actually a problem, then it seems like we would need more resource efficient ways to generate more power. So it might take a combination of renewables to power our cities, then a nuclear process heat from maybe one of the next generation reactors to efficiently create the liquid fuel for ships and planes.