By all means you can buy a new (vpn-able) router and configure it to use a vpn service, just be careful which model you buy and do some homework first to ensure it will work with your isp and vpn provider. Unless split tunneling traffic it would then mean all internet traffic in your house would go through the vpn router - great for privacy, maybe not so much if you are trying to access a bank account or other service where your vpn server may have been blacklisted or use of vpn inadvertently detected as fraud. You would want the ability to easily control the vpn on and off or which programs/ip addresses can bypass the vpn etc... it could get more tricky technically, in setting it all up and configuring it correctly, which is why I suspect a
fire stick may be the easier option.
Fire stick with a VPN app and the iptv player app both installed (duplex, tivimate, xciptv etc.) on the
fire stick. Turn on the vpn. Check the vpn is working (visit google and type what is my ip address and check it is the ip of the vpn and not your isp) and then load up your iptv app and away you go.
There is also another app I use which is relatively unobtrusive if you want added peace of mind that your vpn is working whilst watching the iptv. Google "vpn safety dot" for android. This puts a small slow flashing green dot in the top corner of your screen and simply when it's green it means the vpn is working and if it's red it means the vpn isn't working.
Please check with your supplier before you purchase the
fire stick, they should be able to provide you with login details for the duplex app on
fire stick. If your sub is only for 1 line / 1 device then obviously don't try to run two instances of iptv otherwise this could lead to your service being blocked. Maybe once you have it set up and working okay on the
fire stick then uninstall the app from your smart tv so there are no accidents.