Review and update Get started pages

[edonehoo]

### Tasks
- [ ] https://github.com/patternfly/patternfly-org/issues/3897
- [ ] https://github.com/patternfly/patternfly-org/issues/3914
- [ ] https://github.com/patternfly/patternfly-org/issues/3889
- [ ] https://github.com/patternfly/patternfly-org/issues/3888
- [ ] https://github.com/patternfly/patternfly-org/issues/3921