Indeed BTC has less risks compared to altcoins. However on the contrary BTC is super risky compared to traditional assets. About risks and volatility overall on average it's like this: bonds < stocks < commoditiies < alternative assets < Bitcoin < altcoins.
And isn't it contradictory "bitcoin price has a risk but we can avoid that risk by investing an amount that we can afford to loss"? I am afraid it's not avoiding risk, it's simply accepting it, and actually preparing that this risk will destroy your capital.
There's a reason why investing is the best bet against the future economy, the chances of having much more than your current have is certain most especially when you pick the right investment. Bitcoin is a perfect example of the right investment as it has all the features of a success investment. It has a finite supply which guarantee price increase provided the demand of the asset remains constant or increase with time which from every indications is certain.
I don't recommend any strategy actually, since it can be easily automated, and if so - it's already known and in use by someone who can do it better than any of us and faster. I think, as I noted before strategy, skills or experience are not the things which make successful trader/investor, but the financial instruments they can use. As you cannot invest in million things which are accessible to the elites of financial world.
I think the innovations on trading in the stock market have affected and definitely the same it's just that in crypto, it's 24 hours. No closing in the day or night (in different timezones). It can be called an innovation because it wasn't previously used in that category, but it doesn't mean it didn't improve.
Trading 24/7 is definitely a good thing as it allowed people to react immediately at any time to the new events as opposed to stock markets. And what you refer to about trading anything but top20 cryptos is a valid reason as those pairs have less liquidity, less coverage, thus they have more arbitrage and inefficiency opportunities to be exploited by the ones who are able to do so.