Kubernetes Hosting and Storage Questions

Hello all,

I have a few questions regarding the Kubernetes hosting offer.
Currently I have created a standard cluster with 3 nodes.

Version 1.22
$60.00/month
6 CPU cores --> 2 per node
12 GB RAM --> 4 per node
240 GB storage --> 80 per node

While reviewing the nodes, I noticed that none of them have the Master / Control plane role.

Question. 1:
Am I correct in assuming that this part is managed by Linode ?
Question 1.1:
And if so I have 3 worker nodes that I can demolish and rebuild whenever I want ?

Memory management at Linode:
I installed Longhorn and then saw:

Schedulable 148 Gi
Reserved 70.8 Gi
Used 16.8 Gi
Disabled 0 Bi
Total 236 Gi

Reserved 70.8 Gi --> for each node 23.6 Gi
Question 2:
For what are the 23.6 Gi reserved on each node ?
This would not be 80 Gi as. stated but actually usable. "only" 55.1 Gi
My assumption is operating system and what is necessary to run the node.

Last question: --> storageclass
Is it safe to set the linode-block-storage-retain from default to no ?

NAME                                    PROVISIONER 
linode-block-storage                    linodebs.csi.linode.com
linode-block-storage-retain (default)   linodebs.csi.linode.com
longhorn (default)                      driver.longhorn.io

Have a nice day ;-)