1. The fight will go either way, because Minato has better FTG tech, which means he was able to create his own version of fighting, however Tobirama during his life time could only mark someone else or mark his own blade or kunais, in other words Minato has better advantage since he has a lot of preparations.
2. Tobirama has a lot more battle experience. He can create a massive of water that makes his tech so OP that Minato have to use his S/T barrier to counter it. Pretty sure that Rasengan is not enough to harm Tobirama. Both has a lot of sealing jutsus so it might be possible that Minato takes this one, because his sealing jutsus are known as Uzumaki's...
3. I think the one who mark with FTG first, will somehow win the battle.
Minato > = Tobirama