Illegal to connect without using API? What kind of proxy should I use?

Hi. Been doing some googling, but I can't find the answer. Maybe I'm bad at googling...
Is it against the ToS on social medias (FB, IG, Twitter) to connect without the use of API? I'm currently developing a SaaS website which has a basic post scheduler and stuff like answer chat messages on our dashboard etc. Problem is I'm not using an API for any of this due to limitations(did i answer my own question?).

I'm going to assign 1 proxy to each set of social media accounts (1 proxy = 1 FB, IG, Twitter), which is np. What kind of proxy should I be going for?

if you can build a reliable service people are willing to pay for without an api, go for it, social media wont go after you before you make your first milion dollar

sephialife said:

if you can build a reliable service people are willing to pay for without an api, go for it, social media wont go after you before you make your first milion dollar

Click to expand...

I can, but I'm worried users will get banned because we're not using API. As it's supposed to be a white hat tool, no one would expect a ban. I've only done e-commerce up until now, so this is my first time even trying SaaS. I don't have a crazy budget, so i don't want to blow it already on developing wrong, and have to re-develop later. And I believe a good first impression is important. You can't really bounce back if people get banned during launch and the negative reps start spreading