Since my vehicle is an E-4orce, I am unable to offer any guidance regarding certain aspects of the MHEV. Sure, it's common knowledge that certain 18-year-old diesels can go around the world on a single tank of petrol, but it doesn't really address the point. All I can say is that hybrid driving does require some practice. As is often the case, urban fuel economy is poor, but this is particularly true when travelling at high speeds on highways. It doesn't seem appropriate to get 20 MPG. If you only have a 1.5-liter three-cylinder engine with variable compression, it should be able to handle well on its own. Going back to the dealer and asking them to check might be worth it, in my opinion.
Due to data protection requirements, the startup splash screen is present. Remote applications (like Nissan Connect) would not function without the massive amounts of data generated by the T33 and stored in the cloud, as is the case with the majority of modern automobiles. So, it's not something you can eliminate. There is a legislative component to the speed warning as well. There is no way to permanently disable it, I'm afraid.
If you are able to improve the MPG, please let us know.