I think a few more details would help in providing aa useful answer. VPNs can be used for many purposes - what is yours? Also, a VPN can be run totally separately from your local LAN, with it being used simultaneously with your local non-VPN traffic.
yes it will as long as you aren't using the same ip ports
I have a SoftEther VPN Server on my network for a couple years now I have even ran the VPN Server on my Flex computer works fine just have to have a robust enough network connection