I think season opens up with an IT, Smart, Hayward, Crowder, Horford lineup and a bench of Rozier, Brown, Tatum, Morris, Zizic (as of now; I expect a veteran big to be signed).
But I think the lineup will change with matchups.
Ultimately, Brown will move into the starting lineup at some point next year.
Their best lineup might be IT, Brown, Hayward, Morris, Horford. Gives them most size and flexibity and shooting.