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.