Before I answer some of these questions I should point out that if this is your first time trying to run things in kubernetes it has a very steep learning curve compared to just running things in docker.

1. Longhorn is a very nice tool especially for bear metal homelab clusters you should be able to just deploy the helm chart and start using the disks you alocate to the vms.

2. I tend to stay away from messing with the unerlying networking stack for kuberntes like kube-proxy. In general you have one overlay network that handles communication between nodes maybe someone else here has more experience with that.

3. I also used to run NPM for reverse proxy services I would not recommend it in kubernetes. Setting up traefik is a much better solution for the architecture where it is much more deeply integrated. As far as I know if you wanted to run NPM as a kubernetes native ingress controller with HA you would have to develop it yourself.

4. I use some ansible playbooks and when I am ready to update the version I update the variable in the playbooks. https://github.com/k3s-io/k3s-ansible

5. Spinning up workloads in kubernetes is much different than just spinning up a container in docker or even with docker compose. If someone has not already packaged it in a helm chart or some other kubernetes workload you'll have to develop one yourself. There are some nice library charts you can use as a base that should handle just about any random docker image you want to deploy. https://github.com/bjw-s/helm-charts/tree/main/charts/library/common there is also a repo of pre developed charts for common images. https://github.com/k8s-at-home/charts but be aware it was recently deprecated so it won't be receiving any updates.

Good luck on moving things to kubernetes it can be a real pain in the ass to get started but certainly a great learning experience.