Lump Sump vs Periodic/automated investment & ETF or Index Funds for brokerage account after maxing out Roth IRA? Bonuses for 50K tax account?

I’ve been maxing out my Roth IRA for a few years now. I finished my 2024 contribution in April 2025 (great timing), and now I’m wishing I had also maxed out 2025. I’m not planning to buy a house anytime soon due to prices, job stability, and the general uncertainty in the economy, so I want my savings to work harder.

My plan is to max out both 2025 and 2026 Roth IRA contributions at once, keep about 20k as an emergency fund, and put around 50k into a taxable account. From what I’ve read, ETFs are better than mutual funds in taxable accounts, so I’m thinking 90 percent S&P 500 ETF and 10 percent international.

I also have about 16k in checking and will add another \~5k from PTO cash-out to give myself extra cushion. My monthly expenses are about 5k.

I’m looking for suggestions on brokerage bonuses. I already have Fidelity, but I don’t think they offer bonuses for existing customers. Where should I look?

TIA!