Newbie general questions about Image builder


i'll start to use image builder to custom a few the default image for my Er-x (need some extra packages to connect to my isp )

my questions are very basic

i will build v18.03.4
If i choose with "make menuconfig" and choose only theTarget System - Subtarget -Target Profile of my router will i obtain the same image as the one in the download page (and just have to add the extra package i need) ?

Is the target profile containing all settings and packages for a decent security ?