Reddit mentions of Casio CTK2400 61- Key Portable Keyboard with USB

1: That's just a controller. It doesn't have sounds of its own. I would suggest considering something that does have sounds of its own (such as a synthesizer, a piano, or something more like a normal student keyboard like this) so that you aren't tethered to a computer+software any time you want to practice. That said, you can still get by with a controller only and your laptop. Whatever you get, you probably do want Midi so you can use it with your software. (Unless it's a real 88-key piano, which is probably the best for learning IMO). For the "portable keyboards" with midi support, like the one I linked, Yamaha and Casio make some pretty good ones. A little pricier than the one you linked, unfortunately. 32 keys might feel a kind of limiting, but maybe not. You can probably find a 61-key one with MIDI on craigslist pretty cheap. (Yamaha PSR series is pretty good, nice sounds)

2: Learning some music theory is definitely a helpful tool, and that generally means studying an instrument. It's pretty much essential for collaborating with other musicians, since you'll need to speak "the language of music." (Keys, chords, etc.) One thing I've always enjoyed for learning is going to guitar chord sites (like ultimate-guitar.com), looking up some songs I know, and playing the chords on piano. If you don't know how to play a chord, look it up. You'll start noticing patterns (how to play a major chord, minor chord, 7th, maj7, etc). That combined with practicing scales can take you pretty far, and give you some tools to explore when writing songs. /r/musictheory seems to be a good community for resources, too.

3: Piano is so fun. I played other instruments before picking up piano, but learning piano has improved my understanding of other instruments (and theory in general) dramatically. So I think you definitely have the right idea looking at keyboard instruments.

4: If you do get a MIDI controller that doesn't have built-in sounds.. I noticed that the one you linked doesn't have any pitch bend or modulation wheel. I'd consider getting one that does. Pretty handy when working with synths (including the ones in your DAW). Another nice thing to have is pads for banging out drum beats. Much more intuitive than using the keyboard. Neither are essential, but they're fun, and something to consider. M-Audio Axiom series is a good one with both of these features. Oxygen series, too.

5: Interestingly, Keystation 49 II is the same price on Amazon as the Keystation MIni 32 you linked. Out of the two, I would definitely go for the 49. More keys, and real pitch bend+modulation wheels. (The pitch bend buttons on the mini look kind of lame IMO.) Unless the more portable size is just super important to you.

6: If the keyboard you get has traditional (round) MIDI I/O ports but no USB port, then you'll need a MIDI interface for your computer. They're cheap, and you don't need anything fancy. Something like this is fine. You can also get an audio interface that has MIDI built-in. If you go with an audio interface, you should do more research, as a good audio interface (unlike an expensive midi adapter) does make a big difference in the sound that gets recorded. But that's probably farther down the line if right now you're just trying to learn and get better at composition. At that point you'll be looking at good monitor speakers and/or monitor headphones, too.

No hard and fast rules, here. Just a few things to consider.

For me a good MIDI keyboard has evenly spaced keys with some resistance. Also, the MIDI must be able to pick up velocity levels. I personally love keyboards that have 61+ keys but they can be pricey. Heres one I just recommended in another thread that's perfect.
https://www.amazon.com/Casio-CTK2400-61-Portable-Keyboard/dp/B00JZEW3KC

Depending on your price range, you could also get a really nice Yamaha. Yamaha keyboards with weighted keys are incredible to play on. I have an old PSR E313 and I love it and while they keys are unweighted, the keys pick up velocity well and are evenly spaced. Some people dislike the plastic keys though.

All about personal preference! If you have a music store nearby you should check out some of the keyboards and get a feel for what you like.

Hope this helped! Happy hunting!

Is this a good keyboard for a beginner. Is it a good keyboard for its price?