Killians1978

For most video editing Threadripper probably won't be worth it over a Ryzen 9. Video work is traditionally a multicore task, but most programs don't scale super well above 12-18 cores. Games won't care in the slightest about large core counts, and Threadripper's lower single-core boost clock will hurt you much more than the many threads will help.
 
At your budget, you're right that Nvidia is the way to go. Additionally, current Nvidia cards include the improved Nvenc engine for GPU encoding, which provides good quality while not taking up any CPU usage. That said, on a 3900x or 3950x you'll have enough cores to run CPU encoding anyway.
 
One important consideration if you go Ryzen 9 is that Ryzen really likes fast FCLK (Infinity fabric speed) and memory, which are usually linked. If you stick with your current 2666MHz memory, you'd likely want to break that link and go to 1800+ FCLK instead of the 1333 FCLK that you would get if you left it stock.
 
One thing I'm not super familiar with is how much After Effects etc. like memory capacity. In the parts list I added a fast 2x16GB kit, you could add another if you think you'll want 64GB.
 
Here's an $1800 build I threw together- I didn't include peripherals or monitors because I don't know what would work best for your setup, and you could upgrade to either a 3950X or a 2080 Super for some marginal benefit if you wanted to spend a bit more.
PCPartPicker Part List Type Item Price CPU AMD Ryzen 9 3900X 3.8 GHz 12-Core Processor $469.99 @ Amazon CPU Cooler Noctua NH-U12S chromax.black 55 CFM CPU Cooler $69.95 @ Amazon Motherboard ASRock X570 Steel Legend ATX AM4 Motherboard $179.99 @ Amazon Memory Corsair Vengeance LPX 32 GB (2 x 16 GB) DDR4-3600 Memory $154.99 @ Newegg Storage Crucial P1 1 TB M.2-2280 NVME Solid State Drive $112.99 @ Newegg Video Card EVGA GeForce RTX 2070 SUPER 8 GB BLACK GAMING Video Card $473.98 @ Newegg Case Fractal Design Meshify C ATX Mid Tower Case $98.95 @ Walmart Power Supply Corsair RMx (2018) 650 W 80+ Gold Certified Fully Modular ATX Power Supply $109.99 @ Amazon Operating System Microsoft Windows 10 Home OEM 64-bit $99.99 @ B&H   Prices include shipping, taxes, rebates, and discounts     Total (before mail-in rebates) $1790.82   Mail-in rebates -$20.00   Total $1770.82   Generated by PCPartPicker 2020-02-07 16:33 EST-0500