Keycloak supports both OpenID Connect (an extension to OAuth 2.0) and SAML 2.0. When securing clients and services the first thing you need to decide is which of the two you are going to use. If you want you can also choose to secure some with OpenID Connect and others with SAML.
To secure clients and services you are also going to need an adapter or library for the protocol you’ve selected. Keycloak comes with its own adapters for selected platforms, but it is also possible to use generic OpenID Connect Resource Provider and SAML Service Provider libraries.