Personally, join SpinCo. It's likely to offer NO pension and only 401k match but then your pension would still be managed under 3M (you don't lose anything) - that is until the next Mike (Vale) gets his machete out and carves up remain-co into 4 or 5 pieces.
The lump sum may be better in a few years if inflation calm back down to 3 or under.
I agree with the poster on severance. Hang around, do your best if you enjoy your team, and then volunteer when they came around for cuts in 2 years or so.
Like the other poster, I retired so that I could lock in my pension before the lump sum got a 20 percent haircut.
And, if you can retire completely, just relax. Have coffee every morn on the porch and do any community activities you like.
Haven't had time to research much but does 3M have a vibrant retirees group in the east metro like tartan park and 3M Club were for employees in the 80s and 90s???