If you want to seriously develop keyboard skills, and it sounds like you are not necessarily a classically trained piano player - then you have some questions to ask yourself.

1. Do you want to become a better piano player through practice and exercise?

2. Do you think that you will supplement BIAB through your own soloing on keyboard and using either a built-in to the keyboard sound source or external hardware based sound source, or with a software based instrument? (Based on your response immediately above, I am thinkng that the answer to this question is "No" at least for now.

3. Do you think you will ever gig in a band as a keyboard player? If so, what style do you see yourself playing; classic rock or country, gospel, modern rock, progressive rock, R&B, etc.

4. How is your back? (related question to #3)

All of these questions should guide your choice of keyboard.

Answer to question #1 immediately divides the field of choices significantly. If your answer is 'yes' to question 1, then do not consider any non-weighted keyboards. Period. It's my opinion, and held by many others, that you cannot improve true piano playing skills with unweighted keys if that is your only keyboard you have to practice on. This also somewhat determines the number of octaves you should be choosing. I would not buy anything less than a 76 note keyboard if the answer is yes to question 1.

If the answer to question #1 is "No", then the field of choices is much wider, including weighted keys, but many more choices with unweighted keys and fewer octaves. For some styles, weighted keys are a detriment. For example, playing classic rock and R&B organ; it's better to have unweighted keys for that (my opinion - some do just fine with this, but I can't). I'm actually playing a real Hammond these days (M3 with speaker defeated going into a Leslie amp/cabinet simulator). I also believe synth soloing or even simulated acoustic instrument soloing is better achieved on a non-weighted keyboard (with mod and pitch bend wheels in my case), because that's what I've done for the past 30+ years. In this case, 49+ key keyboards work well, and going to fewer numbers of keys starts to force you into a single-handed technique. For synth soloing, this can actually be just fine if you have handy octave +/- buttons for the free hand. This is one area where the Oxygen 49 layout was pretty great for the left hand; mod and pitch bend wheels at the ready as well as octave +/- buttons right there in perfect position for it. (Here's an image of the silver edition Oxygen 49 where you can see the octave buttons right above the mod and pitch bend wheels https://www.google.com/search?q=oxygen+49&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiGzqa1u7PUAhVJ8IMKHQ87BWIQ_AUIDCgD&biw=1440&bih=765#imgrc=KpSsy7ULZBZWQM:)

Here's a track I did several years ago using the M-Audio Oxygen 49 with only freeware VSTi. At about 4:40 into the track, I'm making very extensive use of the mod wheel (for the filter settings) and the octave +/- buttons to dance across the octaves, and the pitch bend wheel for nuanced wiggle on the solo line. There is a glitch that occurred right at the beginning of the song related to either .mp3 encoding or placement into Soundcloud.
https://soundcloud.com/rockstar_not/rockstarnot-ambishot-2-1

Answer to question #2 seems like you are already answering this.

Question #3; specific to organ. Here's a track where I contributed s some classic rock organ, with an unweighted keyboard and the GSi VB3 plugin. The slides on this song and how fast they were done (I played this live to the track) would have been almost impossible with a weighted keyboard.
https://soundcloud.com/rockstar_not/hitched-collab-jeff-desantis-w-scott-lake

4. Try to get a lightweight keyboard if you are gigging.

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