If someone doesn't want volatility, they can invest in USDC and DAI for a while before the right opportunity to buy Bitcoin comes but at the moment I believe that now is a good time to buy Bitcoins, it will bounce back soon.
Btw I don't understand why would someone invest in 20 or more coins. It's very hard to track the price of these coins every day multiple times but even if you rarely check them, it's still not a good portfolio because there aren't 20 good coins in the crypto world, there are only a few that are worth the investment. My portfolio includes Bitcoin, Ethereum, Solana, Polygon and Cardano. I plan to invest in a few other coins but I don't want to exceed 10 coins.
Volatility is not bad but we can utilize it to our advantage. There are still people that considers stable coins even after that. When it comes to them, you didn't mention Tether (the leading one) . When investing, it must be the earlier the better. Waiting is a myth because we can't tell the future if ever the price that we want will ever come or not.
As of now, BTC have slightly recovered but it still can be considered before more recoveries came in the scene. There are people that loves more. As the saying says: 'The more the merrier'. As long as they have a big capital and a lot of time for managing those, I can't see that as an issue and it can be a good thing in fact to maximize an earning. There are tons of cryptos in the space and there are plenty of them actually that are great too.