Q: Is there a certain YMM search you suggest to integrate with your Turn 14 app?
A: We use Nexus Easy Year Make Model Search ($15 a month) and GoVedia Automotive Part Search ($50 a month) mostly as they are relatively straightforward, and their teams have been excellent about support and integrating with the app. Convermax is a excellent option as well if you need custom search fields or additional sidebar filtering. They create custom searches. That's not to say that you can't try another app if you prefer!
Q: Do you know if the YMM comes preloaded with all vehicle info? Or if I have to add that to the YMM plugin myself?
A: With the above two you can go into the integrations tab of the Turn 14 Distribution app, and there's a clickable link to download the CSV file for the app you choose. This is generated with the filters you have in place in the Turn 14 Distribution app. So once you set up the YMM app of your choice you can simply upload the file.
I have played with both apps a bit and they have some very clear instructions. They also both have excellent support who can answer any questions for you.