Commercial product using a GPL OS

Question

we are planning to create a commercial product. The product consists of some MCUs and a small computer (we are developing on a Raspberry Pi at the moment).

The computer needs an operating system as we would like keep things like WLAN and booting as simple as possible. We created some software that runs on this computer (node.js application).

The most operating systems like Arch Linux are licensed under the GPL.

The product we would sell contains the computer with pre-installed OS and software. This system operates as a central access point to MCU devices and is able to control them.

We use other's software in our product. We do not modify their source code. The product (the computer part) consists of a computer, an OS and software we create.

1. How does the use of an OS affect our own code (licence)?
2. Is there a possibility of avoiding GPL for our own code? eg. shipping the software separated?
3. Are there any effects to other components of our product, eg. the MCU part?
4. The node.js application delivers a WebApp to the client where it is executed. Are there any effects (As we would like to sell parts of the code as an additional App on the App Stores)?

I know we make use of the work of the community and i respect this. The problem is: The software alone is kind of useless without the MCU devices. I do not expect a legal advice.