Generally speaking the Arch Linux Wiki is a great resource - and it applies almost 1-1 for Manjaro Linux → Hyper-V - ArchWiki
Nothing.
If you use the default network settings you are likely using NAT - which will make your hosts network inaccessible from the guest.
To be able to access the host’s network - including any shared folders on your host - you will need to configure the virtual network using bridged network.
As for mounting samba shares see
→ [root tip] [Utility Script] GIO mount samba share
→ [root tip] [How To] Use systemd to mount ANY device
→ [root tip] [How To] systemd mount unit samples
And more on sharing files using samba
→ Search results for '#contributions:tutorials samba' - Manjaro Linux Forum
That will work automagically when you have configured your host to pass in the usb stick.
As for USB passthrough - I have no idea - it is a long time since I used Hyper-V and that was to host a virtual Exchange server for a client.
This is Manjaro Linux forum - configuring your Windows host is out of scope here.