Memory access on byte/word addressable memory
The question is probably about address bits, not data bits.

A 4G x 32bits memory size is 16Gbytes.


With a 8bits data bus, you need 34 address bits (typically A[33:0])
With a 32bits data bus, you need 32 address bits (typically A[33:2]. A[1:0] is for selecting individual bytes inside the 32bits word.)