1. Both are good choice but you don't invest in a stable coin. It's a way to retain the value of your profit.
2. That's too many and too much diversification. I wouldn't do that to be honest because that's almost going to get you nothing. You might earn with one pump from your 2-3 coins but then get a terrible loss from the other remaining coins. So, don't diversify a lot and get at least 2-5 coins of your choice, the ones that you have the strongest conviction of holding because you're going nowhere with that number of cryptos.