Hi,
For the last 3 years I have been working as a web automation architect. I developed solutions driven by selenium.
Selenium allows to manipulate a real browser. I can log in with selenium as a real user. Javascripts, cookies are maintained. Everything which a real user can do Selenium can do either: click on links, buttons, follow by redirects, etc. Screenshots taking is possible as well. Selenium headless work is possible.
So I think that your solution can be Selenium driven.
The solid Selenium related solutions which I developed log in to services, scrap and post data. Some of them worked in multithread mode through proxies. Selenium instances setting up and tuning were done by me. Some solutions, developed by me, have a backend and a frontend. One solution has reports export to excel. One solution has an email interaction chain(read email and react to it).
Regards,
Nik