[Q] Keyboards(comfortable one's) topic

I have used many devices, and countless keyboards.
I frequently swap between Dvorak n Qwerty keyboard.

On android, I didn't find any comfortable.
I use Nexus 7(2012)(primary device) and a Lenovo A516(Secondary device)
I use google keyboard on both device. But honestly I'm comfortable using it on my Nexus 7.
Lenovo(I use it just to make sure, i use a "phone") lags to the core , If typing ultra fast.

I wish i could find a Keyboard.apk that occupies <5MB
but performs really well.

Also i wish to download ( if they exist/challenge to open source developer community )
- Blackberry OS10 keyboard
- iPhone Keyboard (I'm a huge fan of the keyboard, but the phone is too small and too dumb)
- Nokia x series keyboard.

Also let me know, on phone with 512 MB ram which keyboard goes well?