The buy low and hold for a long time is the perfect one, it's literally the best type of investment I have made so far and I am looking to expand on that. My money is on bitcoin, ethereum, and a bit on other stuff but a whole lot, those are unimportant.
It means I will be able to earn staking rewards from ETH soon enough, and even if I do not have 32 ETH there are pools so it's fine. I would like to achieve something like that on bitcoin too but looks to be quite difficult to achieve, ETH is a blockchain related reward, BTC would be another thing. Both of them at at least 5% would be great, at least I would be getting something instead of waiting.
The holding strategy is without a doubt one of the most effective ones that exist, I know that some people believe that it is too simplistic and easy to implement, and maybe they are right but what matters at the end of the day is that whatever you do is effective, and holding your coins for a very long time has proven to be one of the best strategies that you can implement in this market, or any market by the way, so if there is someone that wants to implement a more advanced strategy they should at first master how to hold their coins
Remembered the quote by a famous stock trader: Buying part is easy, the hardest part is "sitting tight" and doing absolutely nothing...
HODL does not answer all questions about how to be profitable in the long run since the unpredictable risks can destroy this strategy suddenly. Swing trading and long-term market analysis are way more profitable rather than adding more stacks on each downtrend, IMHO. Depending on the trading style, each trader should choose which method suits him better.