Understanding and figuring things out

So I am very much a beginner at this and wanted to get some help. So currently I’m trying a project that will use a rtk system (not for drones /pixhawk). My goal is to use the rtk as precise real time gps. Currently as I looked across thousands of website I came across drotek and really liked the rtk gps kit containing the xxl rtk gps and the xl rtk gps. My thought is to use the xxl rtk gps for the base and the xl rtk gps for the rover. Before I want to purchase the stuff I have a few questions. If I buy the kit will I need to purchase anything else or get anything else (besides u-center)? With this kit will I still have access to the google maps function in u-center? Can I use the xl rtk right out of the box and track the rtk or do I have to add another antenna? Are the 3.7 Li ion batteries for the rover rtk? Will I be able to track altitude with this kit or is that only with the pixhawk? Am I able to connect another rover to the base or am I limited to one rover per base? Will I be able to find the distance from the base to the rover? Lastly are there any videos that can help me set things up not only for u-center but also for the rtk gps kit?
Thank you for your help
Sorry about the length