After a period of delays now, is the current plan of the interlopers to have one bigger and more sustained power outage instead of a series in order to make a bigger splash?

Their plan is to take the market down and keep it down, so their use of power outages is contingent on how poorly the financial system is doing and whether they need another round of mayhem on the energy grids, to further demoralize and weaken humanity. If the outcome is as devastating as they hope on the first round, there may only be a second one as a counterpoint to reinforce the idea something terrible is underway, and people cannot count on the infrastructure to support them any longer. That will make everything worse and may be enough to keep their larger plan in place.