re: Is Ole Miss this season going to be our hardest game to win?

No, I don't think it will be Ole Miss.

I'm very worried about the USC game, it's not a home game. Technically neutral site, but it's more favorable for USC. The Trojans might have more fans in the seats in Vegas, than they do in Cali.
Both teams are replacing potent offenses, and trying to fix abysmal defenses. I cringe when giving Lincoln Riley any credit, but he DOES have a proven record of plugging the next guy in and continuing to roll, so I give them the edge on that side. We're HOPING Nuss and the new WRs will be great, but even with Daniels we started slow.
Defense, it's a tossup. LSU tends to have great players on D, can't say we do currently. Maybe we do, and the new coaches will unlock them. Otherwise, USC may actually have better talent on that side.

Otherwise rest of schedule, I think Alabama will still be very tough. The talent is there, they can actually afford some attrition and still be great.

Ole Miss strikes me as sort of an A&M situation with the great recruiting class- if they stumble or don't mesh early, that could collapse badly.

Oklahoma and UCLA will be fun games, I think they're going to be fights.