It's been awhile since I've upgraded from my older i7 and I now plan on doing so. However, I'm a little confused as to the differences between Z370 and Z390... also am I understanding this correctly that both of these chipsets only do SLI 8x 8x? What's the option for 16x 16x?
 
Thanks for the assistance as I'm currently in the initial stages of my research.

Thank you...I appreciate the response and clarification. So my next question is where to find reliable information on the LGA 2066 processors that have above 32 pcie lanes to deliver. I'm receiving conflicting information on websites... would you happen to know where I can look for this?

cneuhauser when you decide on a CPU and start looking at the X299 mother boards I recommend getting the PDFs of the manuals and really digging into how they divvy up the CPU lanes across the PCIe slots and how they manage things like the M.2 and U.2 slots.
 
You will also want to take into consideration of which slots will give you 16 x 16 lanes and their spacing for your bridge

the_Scarlet_one
Ark.Intel.com can tell you everything. Z series motherboards often support 16 lanes. The X Series often have 44 lanes. There are some lower tier CPUs on the x series boards that only have 28 lanes instead of 44.

You need to take the name of the cpu you are interested in, type it into google or the intel website, and review the information from ark.intel.com

Motherboard manufacturer occasionally try to fudge lanes using a PLX chip, to make it seem like the cpu has more lanes than it does, but there is an issue of latency and it does impact the overall performance.

This is why we don't use PLX chips anymore, due to the latency issues and random compatibility issues they sometimes create.
 
Note, this is different than lane switching, which most motherboards employ now.  PLX adds additional PCIe lanes through gate switching on-the-fly to create "extra" lanes that were not previously available through either the CPU or chipset, whereas most motherboards now use some form of lane switching to enable/disable lanes at the expense of other devices (e.g. Enable M.2 slot will disable SATA ports 0/1).  The latter has no impact on performance, since it's simply allocating resources already available to the chipset.