how many pcie slots can i use?

[darchon]

so in the new x299 mobos, there are 5 physical pcie slots but can i realistically use all 5 at the same time? i get confusing explanations and even the mobo support can't conclusively provide me with a solid answer. eg gigabyte has 5 physical pcie slots and their user guide mentions something about if you have a 44 lane cpu you can use 3 slots in a 16/16/8 configuration. if you have a 28 lane cpu, you can only go 2-way in a 16/8 configuration. but is that pertaining only to gpus or all types of cards which means if i had a 28 lane cpu, i'm relegated to only using 2 slots. then they mention something about the remaining 2 running at x4/x4. does that mean i can use those 2 slots regardless of whether i use the other 3 or 2 higher speed slots?

i've googled this to death and i can't find any answers.