Okta is the only solution I've used that gives you the flexibility you need to make SSO not a nightmare. G Suite and Rippling are both very half-baked and integ

Okta is the only solution I've used that gives you the flexibility you need to make SSO not a nightmare. G Suite and Rippling are both very half-baked and integrations are often broken or the granularity you're looking for is not possible (they also both seem to treat SAML as a last resort and would rather push you to custom Oauth or other flows instead, making every integration work a little bit differently). There may be a few others like One Login where this is their entire business like Okta that are also good, I don't have experience with any others.