[Q] How much internal memory can be cleaned? topic

Hello,

as I see there are some kernels and roms, but for me key question is how much internal memory can I gain after removing write protection (I couldn't find such information).
I know that it probably depends on how much I decide to delete, but I would be thankful if someone wrote:
- which applications take most of the space?
- what is "other" in memory management that takes almost 3GB?

Then I will know if rooting etc. is worth the trouble and warranty loss risk.

Thank you in advance.

Regards,
Chris