To answer this question specifically, yes lightning scales to large transactions through Pickhardt payments, but for long term storage of sums, lightning isn't appropriate (though still works). I regularly move 1Msat between my node and a specific peer with a direct channel all the time, and since its a direct channel it's literally free. Lightning is a liquidity network, and in being so, it makes sending payments quick once bitcoin has been set aside on-chain for a lightning channel but the only purpose of doing this would be to later break it up into smaller sums. If your intention is to recieve a large sum and hodl it, why would you put it on the lightning network unless it was already there? Another way of saying the same thing is, if you dont ever intend to spend some money, why would you transfer it from your savings account to your checking account? Lightning is the checking account and debit card of bitcoin, where onchain transfers are more like a savings account.