Two different things. One is a filter (much loved by 4-5 year olds, their older siblings, their parents and their grandparents). The other is a pose intended to make the lips look puffier, because that's supposedly the current thing to do (thin-lipped people either embrace the pose or they don't - but if they do embrace it, they often over-do it).
Duck-face (which can be used at any time without a camera) is a variant of "kissy face" but to an extreme that many people find silly or parody. I think some would say this is "good duckface":
«•Misaki Clare•» on Instagram: “Feelin my curls on a mini Dallas road trip » « » « #selfie #curlyhair #mygoofyass #duckface #dallas #texas”
If you look at the first poster for Gannon (with the GoG selfie in it), you'll see that TS, like many other Instagram people, are exaggerating it (or don't know how to do it properly). Here are examples of duckfaces that people make fun of:
https://i.redd.it/q59s64hxmlb41.jpg
Anyway, it's considered "over" by anyone aged about 25 and younger, and it was not popular among teens when TS was a teenager - so she's adopting a "lewk" that is associated with (much) younger, more immature people.
Pro-tip: If you like to make a duckface, don't link it to your real name on the internet if you are also looking for professional employment (or for people to take you seriously...or think that you are normal...especially if over 30).