LGA2066 processors have 16, 28, or 44 PCI Express 3.0 lanes. It allows a high-end slot configuration with a 44-lane CPU installed, but the exact configuration will depend on the actual number of PCI Express lanes.
The Gigabyte X299 AORUS Gaming 7 comes with five PCI Express 3.0 x16 slot. The second and the fourth ones work at a maximum speed of x4, and the second slot shares its lanes with one of the M.2 slots.
The first, third, and fifth slots work at x16/x16/x8 with a 44-lane CPU, x16/x8/x0 or x8/x8/x8 with a 28-lane CPU. If you install a 16-lane CPU, the last slot is disabled and the first and third ones work at x8/x4 speeds.
The motherboard supports CrossFire with up to three and SLI with two video cards, except when a 16-lane CPU is installed.
There are also three M.2 slots. The first and third ones are compatible with SSDs up to 2280 with SATA-600 or PCI Express 3.0 x4 connection, while the second one supports 22X110 drives with PCI Express interface only.
The PCI Express x16 slots are covered by stainless steel shields, that shield against interference, and also improve the mechanical strength of each slot.
Figure 2: Slots
As you see in Figure 3, one of the M.2 slots comes with a heatsink that can be used with an M.2 2280 SSD.
Figure 3: M.2 slot with heatsink