Hi and welcome to the vMix community

First I'm sure you can use the search feature to find interesting advices from the community as the 2 questions you ask have been addressed thousands of times already.

In short :

- make sure to create your graphics at the same resolution as your vMix project: i.e. if your project is 1080, all your graphics must be 1920x1080 PNGs with alpha transparency. Never use scaling for graphics.

- if you want to learn and understand how to set your FFMPEG encoder for best results, check:
https://trac.ffmpeg.org/wiki/Encode/H.264

- make sure to understand the difference between FFMPEG using lib264 or NVENC (if you own an nVidia graphic card)

if you just want to copy and paste settings you don't understand, I have nothing for you, the internet is full of crappy tutorials and again this forum is a goldmine for advices. Take some time to read it

Have fun!
Guillaume