BTC is highly recommend if you want to invest in crypto wold because as we all know that BTC is the king and no one can fall it down and also btc is good for long term investment it will make you rich if the price will go Up. But Op remember this if you have 2BNB right now then you can also hold it because bnb is also a good coin for investment. But the last decision are yours if you want o trade you le bnb to btc or just hold your bnb.
Actually Op does not need any other alternative suggestions other than converting to Bitcoin or holding 2 BNB for the long term, I think for the 2 options above and the OP can add other assets in the portfolio for the long term, but regarding investment that must be prepared for risk so anything depends on personal decision.