The speed at which El Niño develops will impact several sub-seasonal weather events the most important of which will be the MJO position and Global Angular Momentum. It is not yet clear how these two metrics will evolve for Spring 2026, but ultimately, it will boil down to trade wind behavior across the Pacific. Right now, the trade winds are surging FROM THE WEST, similar to March 2015 (which eventually evolved into a "Super Niño").
I've posted two maps show May-June Precipitation Anomalies for 2023 (left) and 2015 (right). These are the two most recent strong El Niño's and they couldn't be more different in Spring rainfall totals. There is a lot of uncertainty as we move toward Spring 2026.