As to your question about is it easier the second time after already registering, not necessarily.. The challenge is that so many countries are skipping the EES entry for various reasons that other countries feel they need the entire EES process each time.
I registered for EES in Rome. Used the machines, no problem, smooth as silk. When I exited there they glanced at my passport, did not scan it, and waved me through. This created issues later on……
My next entrance at Helsinki they told me they were putting everyone through the process no matter what since they were unsure about consistency. It actually worked to my benefit since Italy botched my exit there was no record of my departing Schengen zone from previous trip. The kind agent took time to document for me.
Summary, expect the unexpected and go with the flow…….