The Sphere microphone hardware has zero latency, just as any analog microphone does. The Sphere plug-in has 0.5 milliseconds of latency beyond the latency incurred by your DAW. Keep in mind, 0.5 milliseconds of latency is the same time it takes sound travel about six inches.
Using the UAD plug-in version on a Universal Audio Apollo in Console mode will generally incur the lowest total latency possible. At a 96kHz sample rate the Apollo has about 1.1 milliseconds of latency, so the total system latency, in this case, will be 1.6 milliseconds. When using the native version of the plug-in processing latencies will generally be higher, although that’s totally dependent on your DAW setup.
When processing audio that is already recorded to disk most DAWs will compensate for the latency of the plug-in so that effectively no latency occurs.