To be honest, most healthy individuals are not missing out on the SpO2 sensor, nor are first-time smartwatch buyers likely to complain about the SE’s lack of an always-on display or some of the fancier health tracking features found on the Series 9. Apple’s latest entry-level watch is still plenty fast, after all, and it can still take advantage of widgets and the bulk of watchOS 10 features. It can also track your sleeping habits and all your basic fitness activities — running,…