Either should work but it depends on the strength/quality of signal for whichever method you use (same as for any streaming). And if you are abroad, you might get charged more for “roaming data” than in the UK (depends on your mobile provider and contract).
If you can, you’re best off finding a bar with free WiFi and settling down to watch it there.
Depends on your UK data provider. If O2 then the 4G would still come out of your UK allowance in Spain but other telcos dont have the same roaming agreement , so you could be stiffed a massive bill (especially with all the extra minutes being added on since this season !?)
As my revered fellow UTSers say by far the best is to get yourself into a bar with decent Wi-Fi, wear the shirt, fly the flag, and sing your heart out for the lads !
… but, if you get the message that ifollow doe work in your region you might have to see if you get some VPN software running and specify the UK and I so that you get a UK IP address