Yun has some pretty good normals for footsies IMO, st. strong, st. roundhouse, st. forward all serve their purpose. Less utilized but still good normals include cr. forward, st. short (xx lp lunge), st. fierce, toward fierce, cr. strong… lots of very good normals.
st. strong is a good anti air in some situations, st. forward also. EX upkicks is obviously good too.
A big thing IMO for being good with Yun is being able to hit confirm consistently off 2 close normals. typically this is cr. jab, st. jab. In some situations, like after a crossup dive kick, a far st. jab can whiff against crouching chars, so make sure you get that hit confirm nice and early.
st. jab is the only light button that will allow you to combo into cr. strong or st. strong, so be weary of that. You can also link st. short from cr. jab, so things like cr. jab xx cr. jab xx cr. jab, st. short xx lp lunge punch is a good combo to be consistent with too. Too many people miss that hit confirm early and just push themselves out when they should be getting a free knockdown from lp lunge.
Learn the character specific max damage punishes (how many strongs can you get, do you need to end in mk or hk upkicks)