Hi!
Doing it that way (repeated installed in a sandbox), is the proper way to learn.
My suggestion is to create an Incus VM in your existing setup, then install Incus in that VM, launch containers, etc. Once you have done your experimentation, delete the VM and start over. By doing so, you would have a nice sandbox that does not affect your system in any way.
Also, see How to best ask questions on this discussion forum for formatting tips.
In your existing setup, you got Incus with 30GiB of storage (storage pool), and that storage has been placed in a file (loop file). The other option is to use a separate partition. For this learning process, it is fine as it is.
When you create a VM in Incus, your VM will get by default 10GiB of space and 1GiB of RAM. This is probably not a lot when you install Incus in there. When I do testing, that amount is fine, since I tend to use images:alpine/edge/cloud images which are tiny in terms of memory use and space. Anyway, when you launch a VM, you can specify different diskspace/memory.
See the First steps of the Incus documentation for your easy questions. For example, you do not need to use sudo all the time. Add your non-root account to the incus-admin Unix group.
You can edit fields like description by setting the appropriate key to the new value or by incus storage edit mystorage.