1. On the Power trace it depends on the current consumption of the IC. You can calculate these using the Saturn PCB Tool.
For more info have a look at this video:
https://www.youtube.com/watch?v=56Fv...ature=youtu.beDiscussion with Eric Bogatin about why return currents flow under tracks ... and more ...Links:- Eric Bogatin: https://www.linkedin.com/in/eric-bogatin-36886...
2. polygons are also used in places where you need to carry high currents or wide trace can be used.
3. From the Manufacturer/PCB tool could calculate.
When you ask the Manufacturer about the stack-up details, you need to mention controlled impedance values and accordingly,
they'll suggest the trace width for a given reference plane.
(Not sure you're particularly asking about RF tuning.)
4. You can place the fiducials on the corner or near to BGA/high pin count IC.
Why? Assembly house uses them.Would you like to support me in what I do? It's simple:- sign up for one of our Schematic and PCB Design online courses at http...
https://designhelp.fedevel.com/forum...3890-fiducials5.Usually Mounting Hole will be connected to GND or sometimes can be left unconnected. Regarding Arduino design, you might have to ask
on their forum.
6. I'm not sure about this maybe others might answer.
7.
https://designhelp.fedevel.com/forum...brication-note.
PS: most of these questions been already answered, so its better if you could spend time and search here before posting which could save you time.