I ordered a replacement X9DRiLN4F+(Rev 1.02) board 2 months ago and still waiting for it so cant give a definitive answer. This will be DataScience + VM machine with 256GB RAM that I will use for pre-processing.

If you did want to run 4x GPU's you would have to use 2x pcie risers for the 2 uppermost x16 length pcie slots and a turbo GPU in the third slot. Could be tricky then managing where to put the 2 GPU's off the board given the EEATX size of this board.

If you can afford them then the ASUS RTX2080ti Turbos would be my choice. I currently have one of ASUS RTX2080TI Turbo + 1 Galax SG RTX 2080Ti (2.5 slot width) + 1x EVGA Black RTX 2080Ti (2 slot width) in a ASUS X99 WS build with a E5-2690V3 + 128GB RAM. Each of the GPU's I bought used or on discount which is why I ended up with this mix. I have room for another ASUS turbo but cant justify buying one atm.

If I was starting out with a new build I would go ASUS or ASRock X99 WS - sure the motherboard and RAM will be a bit pricey (unles you find a local bargain) but E5-26nn V3/4 cpus have dropped significantly in price in the last year or so, the WS boards give you lots of pcie slots, good usb3 support, good ammount of SATA3 ports, m2 nvme slots and your main cost is going to bu GPUS anyway if you plan to get 4.