The role of Liquid is that if I need to move some funds to Lightning, I can do so with far lower fees than from BTC. At the same time, I can also store the LBTC in a secure wallet. If I need to go to Fiat, I can use Lightning via Strike to go to my bank or CC, extremely low fees. If Bitcion volume jumps, it could cost $20.00 (right now it seems to be around $8.00) or more to get into a block, vs. Liquid at about $0.10.
This may change if Liquid volume increases, but for now, low for the short term future.

It probably can be used to re-balance channels, which is a good use case. I believe Boltz does help with that. Also, Phoenix wallet automates that for you I believe. With the splicing feature it can be done very cheaply, no additional onchain tx.

In terms of amounts, I don't keep a high percentage. Just enough to be good for a few months of living expenses.