I saw a question from you about a Level One Play-through of FFIX and I didn't wanna post in the topic bc its been dead for a couple months so I'll answer here. The way I did my level one game I had three character gain EXP from the battles at Pandemonium by killing off the characters I wanted to keep at Level 1 and letting the others get all the EXP which were Steiner, Garnet, and Amarant. If the Virus status does stick with your characters between discs that would be a viable option in order to keep all your characters from getting any EXP and make the battles much easier but it's hard to get virus on all your characters without the Yans completely demolishing your entire level 1 party. You could always try to get Zombie from the dragons in the Iifa Tree too which prevent gaining of EXP but you gotta heal with Tents instead of potions.
