You're side stepping the point by making it all about GTA-V, there are a lot of other games in this world and some of them crap out on the V-Ram long before they run out of grunt.
If they are on a strict budget of £200 I would advise they save up a tenner and get an 8GB 470 or used 1060 6GB, RX 480 8GB or 390/X or 980TI if they can find one for around £200.
https://www.youtube.com/watch?v=S8wyEMnHgaI
https://www.youtube.com/watch?v=zl6AFaB49Mo
https://www.youtube.com/watch?v=obrCnW6Ss2I
https://www.youtube.com/watch?v=nLRF3TJY5qs
https://www.youtube.com/watch?v=07xjiQvb9xE
Just a few off the top of my head. I guess if you don't mind playing at under 30 fps, no probs but I certainly wouldn't want that and find anything under 50 fps quite horrid.