I have a Late-2010 Macbook Air with the fastest processor (2.13GHz Core 2 Duo) and most memory that was available at the time. I upgraded to MacOS Sierra, and I had a horrible time of it. The processor was always overloaded, and the fan was always running. I couldn't even browse the web, because the fan would immediately kick in and the whole computer would slow down.
In contrast, I downgraded back to MacOS X 10.11 El Capitan, and now the same Late-2010 Macbook Air is totally happy! No more processor overloads, no fan kicking in, and I can use Chrome again with no strain. It just works again.
So while Apple says a Late-2010 Macbook Air is acceptable for MacOS Sierra, I would recommend holding off as long as you can (if not forever.) It really cripples your experience.
The 2009 Mac Mini is considered unacceptable for Sierra by Apple, and that also has a Core Duo processor like the Late-2010 Macbook Air, which makes me wonder why the Air was ever considered OK...