I don’t know if I’m experienced enough to answer your questions fully but I will say a few things since no one has responded yet.
The instantaneous accuracy when in RTK mode can be varied depending if you have a float solution or actually getting a fix. I’ve included three links below to other posts with real world results. The one seemed to get 2cm accuracy during “fix” and about 20cm accuracy during “float”. It also takes some time to get to this accuracy. I think you must be away from any structures to ever get a fix. I tried near my house for a few days but never got a fix until I went out in a field. Remember, base and rover must have SNR levels above 45 to at least 5 satellites at the same time to get a fix. Having your rover on the ground will also make it harder. I assume you can put a base station up high, such as on a pole or a building. Even your location on the planet, time of day and the weather can impact your results. Something that would need to be tested is what accuracy can you get if a rover can first get a fix in a more open area and then it moves near a structure. I’ll see if I can get time to try this.
