Well, i dunno about torrenting anything else that rarely download some linux distros... But it depend so much of course your VPN provider and your possible modem and firewall/security port-forwarding settings and many case's if mobile using there is no way got your port open, some ISP has some paid services that you could get port open, but it depends ISP. Then it is of course little security problem have port open, but it's your decision do you want it be open or not. Well, this link doesn't supposed be in here
Security forum and sure admin/mode's can delete it but here are some info not for speed what really depend so many other settings that VPN only, but you can look here some questions & answers =>
Which VPN Services Keep You Anonymous in 2017? - TorrentFreak Btw, i prefer AirVpn.