Yes Rashford is good enough to play for Barcelona but with the present Barcelona's squad I don't think Rashford is good enough to earn a stating role in the Barcelona's team.
This would be a different pattern of football than the one Rashford has been used to but he has the pace and ability to do just fine, I don't think Barcelona will use the buy option later, Rashford future will just be a decent premier league team, but I wish him all the best at Barcelona and I hope he proves me wrong.
Depends on Barca formation next season i think they would be needing someone like rashford to actually fit in to that left wing as a stater but Fabrizio made another post today that it might take a while for him to have his debutt for the club regarding his form.
About the buy option, it’s depending on how he performs .. if he eventually makes a noticeably good contribution then Barca could keep him if not then they have no choice than to let him go while they look for a better option so it’s all upto him anyway.
Rashford will join the Barcelona squad on loan. Therefore, everything will depend on his performances. I believe Rashford will find success in Spain with his style of play, just like Antony. Antony had a great time at Betis. Rashford will surely do the same.