A few questions about android and Xperia Z

Okay so I downgraded from CM11 (4.4) to Stock 4.3 slim rom for GPS functionality, And I am a bit confused about a few things.

1st - I now have Google Now Launcher, It has okay google voice searching, Now I know the Moto X has this ability OOB and it has a special low power core to deal with listening, The Xperia Z does not have a companion core to deal with this, will it affect my battery at all? It only works when I am on my desktop (The launcher) if I have an app open or notification bar down it is disabled.

2nd - My girlfriend has a Nokia Lumia 920, With Nokia home, this is a brilliant GPS app, I prefer it over Gmaps, I currently have GPS Navigation and Maps offline pro, and was wondering if Home is coming to android, I searched it but I am unsure if what I am hearing is true, I hope so and seeing as Nokia is making a android phone, It would seem a good idea, Any info?

3rd - I love my android system to be light weight in terms of RAM and space, now I understand stuff like Google music and sat-nav wont be light, but what are the lightest apps you have used, like the internet browser? With savings mode if possible :)


Thanks in advance people!