There are hundreds of options. I'm just gonna focus on ETH now, I think it's a solid choice.
I agree with your choice, ETH is indeed the right choice of altcoin to invest, because the price of ETH will definitely increase when the bull run occurs, but of course the price of ETH cannot increase very high compared to altcoin below ETH position, but if you really want to invest which is safe, then ETH is the right choice, but if you want to get a big profits compared to ETH, then TON is the right choice for you to invest right now.