Not currently. We focus on stateless HTTP applications but are developing the technology to work for stateful applications as well.
We don't expect you to! You can still use Valence without having "formal" SLOs defined - think of our SLO manifests as a chance to declare performance, just like you'd declare any other resource in Kubernetes. You will have at least some idea of how your application should perform - start there. A good rule of thumb is the oft-quoted human-computer interaction figure: humans notice more than 100ms of latency.
Valence isn't meant as a replacement of the VPA or HPA but a mechanism to keep those core components configured and up to date with the optimal configuration for your application. You could just use the VPA and HPA together instead, but you'd be continually adjusting and monitoring them as your code and workload changes.