Hi Michael,
RX/TX &
/dev/ttyAMA0; does that also mean that/dev/ttyUSB0is also disabled?
/dev/ttyUSB0 is enabled. There should be no issues with using USB radios. However, I can hardly recommend you some exact radio since there are a lot of them. They all have different characteristics, which may not be suitable for your exact project. However, you can check some examples in Ardupilot docs.
Navio2 is an autopilot HAT, and Reach M+/M2 is a GNSS receiver. They are designed for different applications and have different functions because of that.
Navio2 and its Raspbian image allow you to build your own vehicle, configure all peripheral hardware without additional coding, and connect it to Ground Control Station software to operate.
Reach M+/M2 can provide you with centimeter-accurate coordinates in RTK, which you can either collect as points or output to a 3rd-party device or software.
However, Navio2 u-blox chip can’t work in RTK. That’s why it provides few-meter accuracy only. It can hardly be used for mapping. If you need precise coordinates on your vehicle, it’s indeed better to install Reach M+/M2 additionally.
It’s possible. However, it’s not an easy task. You can find a bit more info here.