Wifi: wifi 6 is the latest thing in speed and comes in many flavors like pcie, and M.2. However, that USB model, while one of the cheapest, will work just fine.
Risers: Those are the good ones, they can handle Molex, SATA, and the one you should use, 6 pin pcie.
Motherboard: You are correct to select B250 over the H100 as you can XMP the B250 memory to DDR$ 2400. That ASUS board is good but look at the power supply connections you need. I am using this motherboard with 16GB of memory and doing fine.
Cheaper on eBay.
Frame: Same one I have … some motherboards have a VGA connector that ends up blocked by the posts of the rig. The Fintech board fits without blocking connectorss. Best price out there
GPU’s: Don’t buy these yet…$449 heck the 3070 will be $499 and outperform it a lot. Also Big Navi is coming out next month, the RX6700xt will use less power and mine much faster. Your selection is good but wait in just a month you may find much better AMD and Nvidia cards to buy for nearly the same price.
Power Supply: That’s a good one as power supplies are high priced recently. I find the EVGA 1300 g2 to have the power for many cards at a lower price especially on eBay.
RAM: good, XMP DDR4 2400 best speed
CPU: Intel, gen 6 or gen 7 only, do not try a coffee lake gen 8. The i5 6400T is a gen 6 quad core, so should work just fine.
So, wait on video cards … That motherboard wants multiple power supplies, get a gigabyte fintech or biostar mining board and get a bigger power supply, 1000w isn’t going handle 6 video cards @200w each.