The term "copinglink" was created by Page (who-is-page on tumblr) specifically to draw a line between people who choose/adopt nonhuman identities and actual otherkin/therians.
Here is the post with the original defintion/s.
Later, the term "otherlink" was also added, I believe, since not everyone who chooses to identify as non-human does so in order to cope.
So copinglink/otherlink is still on the "alterhuman" spectrum, but definitely not otherkinity/therianthropy (or fictionkinity).
Those with pages full of "kintypes" (or "kins" as they like to call it), who usually refuse to use correct terminology or educate themselves are neither c-link nor otherkin.
They're simply tumblrkin/wishkin. Mostly teens or kids that want to fit in, treat it all as some sort of trend and have no actual idea what alterhumanity really is.
I've been on tumblr for a long time now and I've seen it all, unfortunately.
"Annoyed" and "bothered" doesn't even begin to describe what I feel when I browse the otherkin, therian, fictionkin, etc. tags on there. For my own sake and sanity, I try to stay away from the tumblr "'kin" community.
There's several greymuzzles and otherkin on there who are dedicated to correct and reduce the tons of misinformation, fluff and general bs, but a lot of tumblrkin just won't listen or will even react aggressively. I run an alterhuman resource blog myself because of that.
(Once I've been blocked after being called ableist and racist for trying to tell someone that they're c-link and not otherkin...)
So, there's definitely a difference between otherkin/therians, copinglink and tumblrkin.