ふくふくふにゃ~ん いの巻

It's easy, but only if you ignore the difficult bits (chapter titles) that are good for learning

There isn't much text overall in this manga, which on the surface makes it seem easy. However, the chapter titles are usually some wordplay on a Japanese proverb or idiomatic expression. The titles have furigana, but some are still difficult to look up because the wordplay puts a spin on the phrase. There's also at least one outdated kanji in there, as well as cultural references to things like the game of Go and the わらしべ長者 traditional folk tale.

Sure, you can opt to skip these titles, but that's where quite a bit of the humor comes from. If you're willing to work through these idiomatic expressions and wordplay, I feel that you'll get far more out of the manga than if you don't -- but this is precisely the primary challenge for a learner. This is why it's kind of hard to give a rating. If you learn what the chapter titles are referencing, you will get a lot out of this manga, but I suspect that most people aren't doing that, given the current difficulty rating of the manga ("10" as of now). If you let those go over your head, then there's not much learning content left, and you miss most of the references that the author is trying to make.

The rest of the text in the manga lacks furigana, so it's not the best choice for a beginner. It's not especially difficult, but again, as of this writing, the difficulty level is "10", and I feel that rating is severely misleading someone looking for a first manga to read. スーと鯛ちゃん would be a better choice in this regard.

Just a cat doing cat things.

I expect most people pick this up having read チーズスイートホーム and hoping for something similar, which will probably leave them disappointed. Although both series are by the same mangaka, this was written in the mid-80s, and there are some significant differences; a better choice for those looking for something akin to チー would be the author's newest work, スーと鯛ちゃん.

That's not to say this series isn't enjoyable, but if you've read the mangaka's more recent works, it helps to go into this series with adjusted expectations and an open mind. Unlike チー and スー, the cats in this series don't "talk", they merely meow, so the story is conveyed through the images. ふくふく's owner and other humans that occasionally appear have the odd line of speech, but otherwise there isn't much language in the story; however, there is a of onomatopoeia.

Another noticeable difference is the episodic nature of the stories: each chapter is a snapshot of ふくふく's day, without any overarching plot. I found these vignettes of cat antics surprisingly enjoyable, and the short chapters coupled with primarily visual storytelling means it's easy to devour a whole volume in a sitting.

It's probably not going to improve your language skills, but if you are a cat lover, it's an easy, relaxing, enjoyable read.