Though Its not really recomended for this type of board the short answer is Yes, though it does need an updated bios first before you drop in that 3900x. Seen people do it before (for testing) on other B350 boards from other manufacturers and i myself have also tested my 3900x on my gigabyte AX370 Gaming 5 (same 300 series chipset) from a previous build before upgrading to an x570 boards so you should be able to do it.
Just be mindfull of your temps and try to keep the inside of the case as cool as you can cause the vrms on the B350 does get a bit toasty with how much power the 3900x is gonna draw, A decent 280-360mm AIO would also help with the CPU temps (the 3900x can and will run way hotter than the 1700) instead of the stock Prism cooler.
There will be some some slight performance difference compared to other boards (B450,550 etc) but thats normal cause your pretty much running the 3900x on a much smaller vrm that it wasnt originally intended/recommended (by AMD) to run the 3900x on, Also if you plan to go through with upgrade Turn off PBO, you dont need it, even on my x570 board i have that turned off cause the increase in temps was just way higher than the performance increase your gonna get.
