Good for simple requests, simple scripts, assertions, and small workflows. Also not bad with the Open Source version if savvy with code as you can do a lot with custom functionality.Free version has limited compatibility with scripts/projects created from the Pro version, but functionality-wise can probably be made up with coding. As such, the free version may not be too suitable for complex scripts or for those who are not familiar with coding as functionality/usability may be limited.
Cypress.io is an alternative end-to-end test framework that does NOT use Selenium. Since I've only evaluated this tool as a possible solution, my estimation of its performance against Protractor is incomplete. However, if you and your team are looking for automation solutions outside of the Selenium scope, then Cypress.io may be a good fit given the problems you're trying to solve.
Compared to SoapUI, we have been using "light" tools like RestClient extension in Firefox, or Postman. Compared to Postman, SoapUI is more simple for WSDL / SOAP webservices, as SoapUI generate all envelop, but Postman does not. For Rest API, I think that Postman is a little above SoapUI, but not too far away.