Google offers a dozen bidding strategies. They fall into two camps: manual (you control bids) and smart/automated (algorithm controls bids based on goals). Modern best practice is automated, but only when you have the right data.
Algorithm spends budget to get the most conversions. Good starting point when you're proving the channel.
Bid to hit a target cost per acquisition. Best when you know your target CAC and have 30+ conversions/month of data.
Bid to hit a target return on ad spend. Best for e-commerce with revenue tracking.
Algorithm maximizes total value, not number of conversions. Good when conversions have different values (high vs low ticket).
For traffic-focused campaigns. Not usually what you want for direct response.
You set max CPC per keyword. Full control. Lower ceiling. Use when you don't have enough data for smart bidding.
Manual with algorithmic adjustment. Half-and-half. Transitional.
Smart bidding needs data. Below 30 conversions in the last 30 days per campaign, the algorithm can't optimize. Starting below that threshold forces manual or Maximize Conversions until you have data.
Adjust bids by device, location, time of day, audience. Useful for narrowing or scaling. Less needed with smart bidding (it does this automatically).