Curious about morphs

The thread you linked describes "warping" or "distorting." The term "morph" applies to a very particular kind of animated effect derived from two or more target images. But it's been set in Internet stone by now that any kind of image editing is a "morph" in the same way that "everyone knows" Marconi invented radio (he didn't), or that the core of a pencil is lead (it's graphite).

There are a variety of warping tools, and they are of limited use in inflation art. Warps will not smooth out the folding and draping of clothing to give that pumped tight look one expects with inflation. And lens-like distortion filters can quickly turn the pixels of an image to mush. The most satisfying inflation effects are achieved by repainting some portion of an image by hand, or with the aid of "generators" like 3D modeling and rendering, etc.

"Easy" is a relative term. If you are well versed with your image editing tools and have suitable practice, then yes, inflation art is "easy." But if you've never used an image editor or other art program, a simple distortion filter will not magically do what you want. Don't let that discourage you, though. If you really want inflation art, you can learn to do it.

GIMP is an excellent app, and it is free. There are other free apps, too, as well as commercial apps that are not terribly expensive (e.g. Affinity Photo).