Does the Ryzen 3900x / x570 chipset have enough lanes for 3 gpus, 1 nvme, and 1 sata ssd? I've read there are 24x 4.0 pcie lanes, but I can't tell if there is an extra 4x slot for an nvme. Thanks!
Check your Motherboard's Manual. It should indicate how many GPU's you can install with NVME devices.
It should describe how many dedicated NVME lanes the motherboard has and how many slots for GPUs you can install at the same time.
Or simply open a Support Ticket with your Motherboard Support site and see what they say.
If you want that much hardware you will probably need to use the Threadripper platform with more PCIe lanes to support more M.2 hardware etc
X570 is best with a high end video card and maybe two M.2 devices along with the SATA gear