Plan 2: Buy BTC, ETH, and LTC. Weekly, regardless of the current cost of each coin. Alternate between coins so 1 week buy 50/50 BTC and ETH. Next week buy 100% LTC. Next week buys 50/50 again.
HODL both obviously.
Also at what point is a hardware wallet required?
Why do you want to buy BTC and ETH,since their prices are moving in the same direction.
Real portfolio diversification means buying various assets,which prices aren't correlated to each other and are not moving in the same direction-up during a bull market and down,during a bear market.
I think that it doesn't matter if you buy BTC and ETH only or BTC,ETH and LTC.It's basically the same to me.
I'm a Bitcoin maximalist,so I would buy 100% Bitcoin and 0% altcoins.