Exeonx :
I'll be going with a LGA 1151 Asus RoG maximus Hero VIII
Unless you are running 64 bit enabled apps such as photoshop, 16gb should be more than enough.
A 2 x 8gb kit is good. In the past, ram speed has not been an important factor in real app performance or fps.
I am planning on DDR4 2400 which is the fastest you can go without using ram that needs to be overclocked past the stock 1.2v.
If, in the future, you think you might need more, you can take a chance with a second 16gb kit, or, you can sell your old 16gb kit in favor of a 32 bit kit.