Baldwin+3 sounds reasonable. On the one hand she might do better because even Tony Evers, who seems like he'd have less crossover appeal, won by around that much. Otoh, Baldwin's running in a presidential year in a federal race, meaning more intense polarization.
Eh, I don't think Baldwin is an unbeatable titan, but Hovde is a pretty obvious carpet-bagger and Baldwin has a pro-Wisconsin brand around many corners of the state.
This is the same Baldwin who defeated a popular former governor in 2012 by 6%, and 11% in 2018 (an election with 61% turnout, mind you). With those numbers, Hovde would have to flip a large number of voters just to get to 3%. I don't see that happening, I think Baldwin wins by 6-10 regardless of the Presidential margin.
Slotkin 2-8 seems reasonable, probably ends up closer to the higher end of that.
It wasn't obvious at that time, but over the next 6 to 8 years it quickly became obvious that once a governor has been out of office for some time, their appeal on the voters begins to wane. See also: Ted Strickland, Evan Bayh (who was also a former Senator), Phil Bredesen.
In fairness, Bayh ran against the national environment. And Bredesen and Bayh were both from states that lean heavily towards the other party. WI was always more purple and very much open to both parties at all levels.