Hi, will I loose performance if I install my GPU in the bottom slot? I just want the MB LED to be visible and not covered up by the GPU.
Potentially not, but that depends on your graphics card.
I would:
Put the graphics card in the slot 1
Cut a fiber optic cable and use electric tape to tape it to the light on the motherboard then tape the other end in a spot that is out of the way and easy to see.
Don't move your card, move the light.
But honestly, Unless you EXPECT to have issues I wouldn't even use the fiber optic cable idea. I would just put the card where it's supposed to be and expect the computer to work fine and to never need to look at the motherboard light.
Perhaps you could use the second "PCIe 3.0 x16" slot which I guess is the 4th one but I would look at your motherboard manual before doing that.
Bottom slot is 2.0 PCIE X16 , so wouldn't be hardly any loss in performance. https://www.pugetsystems.com/labs/articles/Impact-of-PCI-E-Speed-on-Gaming-Performance-518/