Once you're satisfied v2Ray works properly you can use systemctl to stop or start it:
~/Downloads
❯ systemctl start v2ray
~/Downloads
❯ systemctl stop v2ray
Of course you can also enabled or disable it from starting when your system boots:
~/Downloads
❯ systemctl enable v2ray
~/Downloads
❯ systemctl disable v2ray
Removed /etc/systemd/system/multi-user.target.wants/v2ray.service.