Installing 2 GPU's + Sound card drop second card to 4x Lanes?

lp231

Splendid
No, it won't make the 2nd gpu to run at x4.
First 2x PCIe x16 is at x8/x8
The 3rd PCIe x16 runs at x4 and it shared with the 2x PCIe X1 slots between the first 2 PCIe x16.
Install the sound card on the very first PCIe x1 slot or
at the 3rd PCIe x16 slot.
PCIe x16 can support cards its size and smaller.