A rose by any other name does not change the fact that its still a rose

[shikamaru]

- What form of currency do they use ?

Some use gold and silver coin. Others continue to use FRNs.

How do they avoid taxes at the store counter?

If you produce your own stuff for your consumption, what tax is there to pay?

Taxation, in many instances, is assessed against income. Avoid income.
In many instances, you'll just pay the tax. I, personally, have no objections to this form of taxation.

Do they receive benefit of a postal service delivering to a house address?

This I am not sure. I will have to follow up with them.

I ask these questions because it seems quite impossible to " get completely out of the political system ". It might be that getting out is just an illusion, or that we were never in it to begin with.

A very fair statement.

Avoidance is always a right.
To attempt to drag you into a forum by coercion and fraud is unjust.

I would skew towards treating government at "arm's length" at all times.

I would think they would leave you alone at some point because the administrative and opportunity costs will exceed whatever revenue they could extract from you.