New miner, rig & pcie usb riser questions

Hello everyone, I happend to accidentally learned about zcash after I started trading Crypto currency again and bought a 1080ti. I looked into mining eth since i was trading eth and btc, researching that brought me to the conclusion that zcash is my best bet.

I'm looking at getting 3 more 1080ti's, 4 in total, with the profits/initial investment from trading.

Atm I'd like to run it in my main gaming rig until I get enough cash to build a dedicated mining system.

My question is will a pcie usb riser work with the 1080ti cards? Will it bottle neck on a pcie x1 2.0 slot? should I opt for building 2 rigs and running two cards per rigs?

I was also looking into the asrock btc boards with the 5x pcie x1 2.0 slots and running all four cards on that system with a dual psu setup. Would this be a viable option?

I apologize for grammar and punctuation. English is not my strong suite and I'm writing this from work while on the assembly line between parts.