I have had several of them over the last 20-30 years So here is my advice
First: Some come with a bunch of "Accessories" like air pumps and such. I woudl not waste money on those if I can avoid it. Though a work light is good and a 12 volt accessory outlet handy as well.
Now; I have had small ones (like 600 amps peak) would not even jump a motor cycle, let alone a car.. I think 750 is the minimum for Cars. but even that is b orderline.
My current one was about 100 bucks at Auto Zone and is a 900 Peak Amp. it WILL (And has) started my car. It will start my Motor home or the generator which then can start the MH after a bit of Run time. It also had enough Reserve to run my main slide in and out when the controller crapped (i have a new controll system now but another issue. which will soon be addressed).
So I would suggest 800 amps peak or more
My first one was 1,000 peak amps. That one was nice.
My current one .. the manual say scharge for like a day and a half before use and then charge for at least 12 hours every 3 months. Or after EVERY use .