I don't know enough about importing capacity in that other grid since they're hooked up to the western half supposedly but I agree with your points. TX being hooked up to the rest of the US could have saved them and this other regional grid appears to be managing it better than TX.
That is debatable. Close grids could not have supplied 30GW of power, they were also under near record loads. You would have had to pull from many states away which is insanely inefficient.
Also people miss how big the TX grid is. FL and PA are the #2 and #3 power generation states. TX produces as much as both added together.
