I think that generally the version is started from A then B, C...
So I think M is newer than G.
You can see the Revision History
Page 42 of Rev.G
Page 41 of Reg.M
According to the Revision History of M
G was submitted 10/13/2016 and M was submitted 07/05/2019.
So my bet is M is the newer.
And for the difference(s), please refer to the Revision History of M (Page 41 of 42).
Yea, I did not noticed it.
But when I re-checked them I noticed that
The G version states
Automotive PSoC 4 : PSoC 4100S Family Datasheet
And the M version states
PSoC 4 : PSoC 4100S Datasheet
So although both of them are datasheet of PSoC 4100S,
one is for the standard version and the other is for the "Automotive" version.
I get it now! This is my first time using PSoC so I missed the details.