I've always thought of the Sixers as a bogeyman of sorts, especially on this site. Without Simmons it's gonna be a struggle for them to guard our 4-headed dragon. Horford is cooked, and Harris and Milton are very eh defenders. Richardson can only guard one person. Thybulle is nice on defense, but his offense is putrid. How much time will Thybulle actually get if he's a nonfactor on offense? I don't know. I think winning in 5 or 6 games is a fair prediction.
Amusingly, I think the Sixers thought of the Celtics as a bogeyman coming into the season. Embiid has said something similar in the past.
Anyway, I agree with a lot of what you said here. With Simmons, their defense matched up with us pretty well. He can switch 1-5 and is their best option on Tatum. But without him, the matchups start unraveling for them. While I'd stop short of saying that Horford is cooked, I do think his ability to defend the perimeter has fallen off sharply. He should be overmatched against our wings. Philly will have to send some help his way, and that will unlock some things for us. Coach should have some fun with that.
At the other end, Embiid is a problem when he's healthy but I feel like their offense is a collection of one-on-one players. Their ability to make each other better is limited, and I don't really fear their team off the bounce. That said, their ability to space the floor will improve with Simmons out. Crowding Embiid while also closing out to their shooters will be a challenge for us.
Looking forward to it.