I upgraded mine with this
https://www.newegg.com/Product/Product.aspx?Item=N82E168202321622400 is as fast as its going to go. I tried faster and its just not going to happen due to BCLCK straps.
I first tried the 2800 and tried to force it and ended up ripping my brand new laptop apart to get to the cmos battery.
With the 24 GB you are going to have to replace all sticks which means cracking the machine open to get to the two slots that are not in the user service bay. If you had the 32GB you could just add two Hynix or Samsung sticks to the slots in the service bay.
you can read up about my trials and tribulations here
https://rog.asus.com/forum/showthread.php?82247-G752-(fastest)-memory-upgrade&highlight=g752+fastest...
“Two things are infinite: the universe and human stupidity, I'm not sure about the former” ~ Albert Einstein