With the handset you can display a choice of gauges, data log, immobilise the car, check for error codes etc. Unlike with the M380, there is no alternative map or choice of ‘track’ (no pops/bangs) this is deliberate as there is no chance of the wrong map being loaded with all the M400 hardware installed and thus putting the engine at risk.
If you’re nervous of plugging it in and going through the menu then get with someone who has the same (M380 or M400) and go through it with them.
JohnD