Liquid network is a stable coin that is pegged to bitcoin. It involves pegging in & out bitcoin 1st layer. Running both doesn't seem to work well on a raspberry pi. Beefer hardware needed. You can put the coins on a hardware wallet like any coin. It'd about as fast as like ethereum.

Lightning is more just software that involves people locking bitcoin with each other & sending I-owe-yous back & fourth before they really finalize a bitcoin on-chain transaction (channel close). You need a node running to access your lightning funds. Most people don't want to run their own node because it involves managing channels (using bitcoin on-chain to open channels) so they use custdians which isn't ideal for soverinty/privacy. Lightning takes seconds to send transactions & programs can use it do do things like split payments & streams sats @ have addresses.

LIQUID is more user friendly but lacks support on swaps/exchanges. The average person doesn't even know about bitcoin second-layers & this stuff is niche