In this highly detailed video tutorial courtesy of Tony & Chelsea Northrup, the Sony A7r IV will be covered. He breaks the camera down step by step and really does a fantastic job as always. I highly recommend checking out this video if you just got the Sony A7r IV and are looking to learn how to use it and get the most out of it. Tony also provides best practices and several real world tips and tricks that you will not find in the manual!
If you are looking to really get the most out of your Sony A7R IV, then you must consider some addition optics for your tool chest. All the E-Mount Lenses available will work, but the the full frame E-mount lenses will give you full sensor coverage where the APS-C E-mount lenses will only work in crop factor mode which will not utilize the entire sensor. This might be what you want if filming in super 35mm mode though. You can also use lens adapters and utilize almost any lens on the Sony A7r IV which is quite awesome. In general the native Sony e-mount lenses work best though as far as autofocus accuracy, speed, and features like Eye-Af for example.
The Sony A7r IV has pretty good battery life overall, but I still recommend getting at least 1 extra NP-FZ100 battery for those long days of shooting or recording video. You can also opt for a VG-C4EM battery grip which holds two batteries and also helps with the ergonomics when using larger heavy lenses.