Will everything work correctly when connecting a PCIe x4 SSD to the GIGABYTE P75-D3?

Question

Iron

I want to buy Maiwo KT016 (PCIe to M.2 adapter) , since there is no M.2 on the mother and some Samsung 960, 970 EVO / PRO . There are two questions:

1. Now I have a PCIe 3.0 x16 slot occupied by a video card , if I connect to a free PCIe 2.0 x16 operating in x4 mode , will the speed of the PCIe 3.0 x16 slot be cut down (that is, will the performance of the video card be reduced )?
   
2. After modifying and updating the BIOS (I plan to use the @Bios proprietary utility , I already successfully updated to a new version once), is it possible to clone the OS partition using some program to a new SSD from the HDD, without a clean installation of the system on the SSD? Now the system is installed on an HDD with a GPT partition table using the AHCI protocol (that is, everything corresponds to the correct operation of the SSD, as I understand it).