You face the decision that many of us have faced in this complex, confusing DP market - what's the best DP for me give my needs, wants, and constraints. And you are doing it the smart way. Rather than just diving in, you're asking good questions from those who have walked the same path.
IMO, the key next step is... Asking more questions! You've gotten some really good feedback in less than 24 hours. If you're like me when I walked this path about seven months ago, you're realizing that the answers you've received clarify your thinking AND generate new questions. To some extent this question -> answer -> question growth path will continue. That's inevitable. So how do you know when you have enough information to make a good decision. That's difficult.
Rather than try to gather more information about DPs, I'd suggest that you think about "what's important" given your wants, needs, and constraints. Let's start off with one constraint you mentioned - "apartment". That's pretty huge.
People who live in apartments (or with spouse, kids, and/or roommates) have a noise limitation. Which probably means that you will be practicing with headphones plugged into your DP. I have a Casio PX-850 (see pic below for reference). Since my wife doesn't like the god-awful sounds I make while practicing, I use headphones ALL the time. But that's my situation...
How often will YOU play your DP with headphones? Virtually all the time? If so, what difference will a great DP amp and speakers make? Will the sound quality of a PX-150 (Casio low-end) be different from a PX-850 (Casio high-end)? If the DP amp has 1000 watts, 10 speakers, and a subwoofer, will you hear any difference in your headphones? Highly doubtful.
You've said that you want good piano sound and action in your DP. This is where it gets difficult in the price range that you mentioned.
I can't comment on the others, but my PX-850 sounds pretty good, but not as well as it could. Notice that I have it in a niche with a shelf on top. Which means that the lid can't be raised. Which means the sound isn't as full as it could be. That is my constraint. Your constraints will affect how good your piano sounds. Think carefully about where it will be placed and whether you'll want a shelf or something else on top.
Regarding sound, another consideration is how good you want that piano sound to be. Decent? Very good? REALLY close to an acoustic piano? Unless you are willing to spend thousands of dollars on a DP (and maybe not even then), the internal sounds of almost any DP will be no where near as good as a software piano.
I have Galaxy Vintage D and VILabs American Grand software pianos. The sound is so much better than the native PX-850 sound that it's not even comparable Both are rich and full with a sound that is close to a grand piano. Several weeks ago, I stopped by a Kawai dealer and played a CA95 - an excellent, high-end DP - using headphones. The CA95 keyboard action was excellent but the sound in the headphones no better than my software piano sound.
So a big question is, are you comfortable with adding a computer to your DP? It's not a trivial effort, but the folks here on the forum can help you with setting it up. It adds to the cost of your DP, but the sound quality, expansion features, and potential for growth in the future (like DAWs, other piano software, better speakers, etc) make it a worthwhile option to consider.
Which brings me to my last point - keyboard action. As long as the keyboard has a USB or MIDI ports, you can expand it. OTOH, the keyboard action is what it is. AFAIK, you can't upgrade the keyboard action. If you can, go compare the action of the Casio, Yamaha, and Roland keyboards you are considering with a Kawai CA65 or CA95. I tried out a CA95 and my fingers said "Oooooooh... This is NICE!" I think my Casio keyboard action is good, especially at the price. But the CA95 was WAY better. IMO, try to get the best keyboard feel that you can afford.
As I wrote above, what's most important is how all of this fits with your needs, wants, and constraints. Great sounding features become useless, wasted features it they don't fit with you.
Good luck with your decision.
p.s. IMO, the Kawai VPC-1 is the first wave of the future. In five years (or less), I believe that you will see similar keyboards from multiple companies.