After some consideration I decided to change my approach to the backstories/origins for multiple reasons.
The problem with old backstories was that they all went pretty similarly on "increase or decrease bunch of stats", which didn't offer a very engaging gameplay, so I decided to change them for 'castes'. Basically, from having pool of unique stories assigned to generated characters, we will have few archetypes: 'slavery', 'poor', 'royalty' etc. These archetypes will be influence starting stats, ie royalty will have higher mentals and better looks, but lower obedience and such. It will be somewhat linear, so at start you will be mostly seeing poor and weak slaves, but as you progress, you'll move onto better classes. This has multiple implications:
Easier than origins
More straightforward gameplay mechanic
May be filled with fluff later
Stat diversity is simpler to achieve
Backstories would make for a more interesting mechanic
So, as you can see, its mostly gameplay + implementation vs immersion. On the other hand, traits will still be more varying and archetypes will be affecting chance to get good or bad trait.
Now onto platform, I've tried out various godot options. Basically, first of all we will be using different versions for different platforms (windows, macos, linux, etc). There's an option to export to html5, however to make it easily accessible for everyone, I'd need personal server because of browser security reasons... As I currently don't have it, and have pretty vague understanding on how it will be working for everyone, I will leave this option open for bit later.