Ryzen 3600 is the best CPU for the money right now, hands down. You don’t need an x570 motherboard for it. You would do fine with even a budget b450 board (the b450 tomahawk is quite a good one) or the upcoming b550 boards if you anticipate wanting to upgrade your CPU at a later date (b550 will be released on June 16).
Editing 4k video will take advantage of 32gb of memory. Don’t skimp and get less than that. Make sure you install the ram to run in dual channel mode by separating the dimms as indicated by the manual.
As for Graphics card, AMD cards run really well in Vegas, you would do well with a 5700XT or if you want to spend an extra $100-150, get an Nvidia RTX 2070 Super.
For power supply, you should be able to run all this effectively on 500-600w. Try to get a gold or platinum efficiency if you can afford it, but power supplies and motherboards are seemingly in short supply right now, due to shipping slowdowns from China and increased demand worldwide due to quarantine and government stimulus.
Don’t forget a fast SSD for editing (get the largest M.2 NVME drive you can afford), a sizable HDD for long term storage, and an external HDD for backup!
—– Christian Wheel —–
Radio Host, Los Angeles/San Diego/Nationally Syndicated
Audio Production & Imaging
MS Visual Studio Developer
After Effects Enthusiast