If Crowder wasn't here, I'd guess Ron Mercer lite. But love Crowder and fully expect a Smart-like first season (stats wise, prob in fewer mins).
Isaiah will continue to get his 20+, but I'm not sure Horford even cares about putting up elite stats at this point. He can definitely reach the same ~15 ppg as last year (with greater opportunity), or he could drop slightly given his age and the atmosphere of the West.