My friend wants to fly JetBlue because it's cheaper than delta, a whole 1 dollar. And plus we'd get in about 5 hours earlier.

JFK-SDQ.

Just curious what to expect, as I assume a lot has changed in the past 10 years. I paid for the extra space seat.
From what I gather I am only allowed 1 carry-on, not like on Delta where I can bring a carry-on and a personal item (laptop bag). Read over the website but it doesn't specifically say yes nor no unless I read wrong. So if anyone would be kind enough to clear that up for me I'd appreciate it greatly.

I never had issues with JetBlue in the past expect that 1 time, they almost put my mom onto the wrong flight back in 2017. But I personally never had issues just preferred flying Delta due to first class seats.