What is the difference between the trial and Pro?

There is no separate free plan. You start with a trial, and during that trial you use every feature of Pro. That doesn't change once you upgrade.

The only difference is the counter: your first 10 quotes sent to a customer are free. It counts when you send a quote, not when you draft one, so you can create as many drafts as you like. Once you've sent those 10 quotes, you pick a paid plan to keep sending.

Not sure which plan fits? Watch your quote volume during the trial. Already sending a lot? Business, with 300 quotes per month, may fit better than Pro's 100.