18, looking to get into investing. Where to start?

Hello all, I just turned 18 and am now old enough to open my own brokerage/investing account. I was wondering, where is the best place to open one?

I currently have Bank of America and from my understanding they have a separate company called 'Merril' where I can open an investment account. Is this a good route to go or are there other banks/apps I should go to instead?

I posted here before and I got a general consensus to invest in stuff like the S&P500 for steady growth (VOO, SPY, VTI) and I was wondering if this was the best route to go.

Should I put most of my money into the S&P 500? If so which index fund in particular (VOO, SPY, ETC) is better? Secondly, if I were to invest a small amount into other stocks, where should I look? Google, AAPL, NVDA?

I was also going to open up a HYSA with Bank of America soon as well to put most of my money in as I will be able to retrieve those funds easier. Whatever goes into the index funds will stay there.

I was also wondering what the difference between an ETF, index fund, and mutual funds was? Whats better to invest in? If I were to invest separately into all, which etf/index fund/mutual fund specifically would be best?

I have done some of my own research but I also wanted some guidance from this subreddit as I know you guys are much more experienced.

Thank you all.