The standard two slot SO-DIMM laptops can support 32 GB now thanks to 8Gbit DDR4. There was also 8Gbit DDR3 that is less common and more expensive, but is supported by Broadwell for example.
Yes, but Apple use LPDDR* ("LP" for the low power variant of RAM)
I know, the point is that many standard laptops that are not particularly light or heavy can take up to 32GB of RAM now.
And how is their battery life?
The intel chips support 32GB of LPDDR3. Unfortunately apple doesn't sell a 32GB version, not sure how that's intel's fault.
Intel ARK specifies 32 GB as max memory, but dependent on memory type. For DDR3 is 32 GB. For LPDDR3 maxes out at 16 GB.