I consider Lightning/ecash the same ‘layer’ where Lightning is the clearing mechanism for any ecash token. For simplicity of the post, I just focused on ecash. 

The usefulness of the analogy is that while you have certain limit of power output (base layer), you may need different points of ‘leverage’ to best meet different conditions. The analogy shouldn’t be interpreted beyond that comparison.

I view ecash not as ‘money’ (Bitcoin is the money) but more as a payment instrument (gearing mechanism) that enables you to take advantage of different transaction requirements and payment conditions. In the end, it should all be settled back to a UTXO. As for Liquid, I’m not that familiar with it, but I suspect similar concepts apply.