When posting your novel, you'll find that different platforms skew in favor of different subjects. On Tapas, romance and all its subgenres do very well. On RoyalRoad, fantasy (particularly isekai and rpg inspired stories) is the main draw. And Wattpad, romances with 'bad boys' get a lot of attention.
I've been with Tapas a long time, even before it started hosting novels, so I'm a bit biased. But I think authors have a good chance of building an audience here. There isn't an insane amount of competition like Wattpad, so your work won't get as buried.
And how much you post depends on what platforms you're on.
Tapas likes smaller sized uploads, since the majority of readers are on mobile. Pros: since you're posting smaller parts at a time, you can have a larger buffer. Usually my manuscript's chapters can be split into around 4 Tapas episodes at around 800 to 1k words an update.
I know readers on other sites like to read whole chapters at a time, so best to check out the works that do well on each platform and follow accordingly.
It's always better to build up a following and try and get them to buy your work that way. Even if they cannot make a purchase, they might share your work and you can expand your reach that way. Build an audience, build up hype for your work, and you will have a better launch than publishing something on Amazon cold with no following.
Advice: If you are looking into traditional publishing, check out the publishers you want to shoot for. Publishers will not sign a work that has already been self-published and made available to purchase (unless its numbers are outstanding). This can even extend to works published on webnovel sites, but some publishers are more lax about it.