So are you saying the G512Li has 2X memory modules, one at 3200mhz and the other at 2666mhz? If that is the case, maximum memory speed will be the maximum speed of lowest module. That is........ if they play nice together.
I looked at the user manual for the G512LI, and the BIOS settings are vague at best. So I am not able to establish whether the G512LI BIOS has memory XMP settings. If it does, then set it appropriately. Given this is a ROG laptop, I would have to think it would have some advanced settings in the BIOS.
You say you purchased a 32GB kit now to replace the original miss-matched 3200/2666 modules. According to Asus, these modules should run. Maybe check the memory QVL list and ensure your kit is listed. Even if the memory isnt listed, that does not mean the kit will not work. It just may not have been verified.
Push F2 at post to enter BIOS and check all BIOS settings to see if there is an XMP setting or DRAM Speed setting. If there is, set it appropriately.