Re: difference between seafoam and carb cleaning
If I have a really nasty carb I always used Berryman's Chem Tool in either the spray or the liquid. Really bad stuff and paint hates it, so do your hands, makes them crack with no natural oil left.
I think if you have a varnished carb, SF will do nothing for you. I have restored what I thought to be beyond use equipment, especially 2 cycle with it, but none of the "been sitting 2 years" stuff. Worked great for what I use it for, but I used a lot more than the recommendations on the can, initially. Never did/had to do the "decarb" procedure you will find on here in the archives section.
Worst thing in SF is Naptha (paint thinner per se). Worse thing in Berryman's is like Acetone, or MEK or bad stuff that really attacks crud.
HTH
Mark