I was thinking about starting a second account to have a buffer while I farm for items. After looking over some of the available buffs, I am thinking either a Grand Majin or an Ultimate Majin.

I wanted to ask the community which you would chose and why.

I would say it depends but ultimate has better buffs IMO. They have more pvp buffs wich are useful.

PvP buffs are not what I am shooting for though, this is a farm buffer. PvE. Another question I had was Enchanting Breeze and Miraculous Fitness. Are they able to be up at the same time, or must I chose one or the other?

I recommend a Ultimate, serves more for PVE things, the cheft is for more specific things.