I would say that the most important part of a vintage/comfy shirt is how the ink feels on the shirt. Plastisol is thicker and will not be as good at giving you that soft vintage worn-in feel. Waterbased or discharge ink will blend in nicely with the material and give you the look and feel that you are going for.

BUT plastisol is a lot more forgiving when you’re a beginner and pretty much will never dry out in your screen. You’ll have to be a lot quicker when printing with waterbased.

I’m not as sure on what brands/specs to look out for. Maybe you could post your question on our facebook group for that answer?
https://www.facebook.com/groups/screenprintingathome/