Sorry for the late response, I didn’t get any notifications. “沙雕图” usually refers to funny gifs or images, “沙雕(帖/贴)” could mean stupid or funny posts. “梗” can be translated into memes, so “梗图” refers to meme images.

As for shitposts, I would say “水贴” comes pretty close to the meaning. “水” or water means “low quality” when used to describe something, like “水货” (low quality goods), “水贴” (low quality posts).

Regarding the usage of “wife”, some people like to call public figures that they follow by the term “wife/husband”, this includes video creators. It’s a part of fan/idol culture, the Japanese equivalent “waifu” is similar in this regard.