Ok so to explain this post in detail I'm gonna split it in two parts, one explaining the DX12 and the other with the frames.
Before you use DX12, make sure that you have it on your PC before using this command (mainly Windows, sorry Mac users!). For DX12, you will need to make a shortcut of the "veadotube mini.exe". Reason for this is so we can use that command "-force-d3d12" in the Target when you open Properties of the shortcut. Paste the command after the quotations, and you're good to go!
For the 60 fps way, the way I did it was through the NVIDIA Control Panel. There may be other ways, but this is the way I found for NVIDIA users. Open the control panel, go to "Manage 3D settings", then click the Program Settings tab. From there, you will click Add, and then search for the veadotube application. Then, scroll down till you see "Max Frame Rate". Click it, check on, and then set it to 60 frames.
Hope this made it a bit more easier to understand!