Yes, Holmgren won SBs as an OC in SF, won as a HC in GB, and it could be argued that he won one with Seattle, but it was taken away [which I didn't mind, had money on the Steelers].
Favre threw a lot of picks after Holmgren left. A good HC can reign a guy in. Favre had 24 TDs/29INTs in 2005. Then in 2006 he got what would be his 1st SB winning HC since Holmgren [except McCarthy got it with Rodgers], and Favre went from 24/29, to 18/18 in 2006, to 28/15 in 2007. 2007 Favre got a playoff win, then a NFC Championship loss in extremely cold weather, where it wasn't his throwing INTs that led to the loss, mostly NY Giants run game and Eli being clutch.
Favre played above his norm in the regular season 2 years later, motivated, but having a bad HC, Favre went back to throwing a pick to lose the NFC Championship at home against the Saints.
I think Favre could have been reigned in and won another SB with the right HC. He probably would have won another SB with GB in 2010, had it been him instead of Rodgers, that team was a powerhouse. We will just never know.
SKOL to the BOWL !!!