Yeah, the trick with both liquid smoke and fish sauce is to use way less than you think you need. You'll notice I'm only putting a teaspoon in about a full cup of marinade, and that's enough to give a very distinctly smoky flavour. You can easily cut that back to a half or quarter teaspoon if you prefer it more subtle.
For fish sauce, I'm going to start out with the same kind of measures. I'll probably go with 1tsp and then adjust up or down from there. If you can taste the fish sauce in the finished product you've used too much. And yes, brand absolutely matters. I only ever use Squid brand fish sauce personally.
For anyone looking for a cheap home made jerky method that can be done in regular bog standard oven, try this pork teriyaki jerky method. It's super simple, and requires no equipment.
https://youtu.be/NGMIIGpo5Zw?si=MpI41_o9we-3ej89
Edit: Also, keep that bit about pork tenderloin to yourselves OK? Definitely don't let anyone know that it's a ridiculously cheap cut that you can use to make an absolutely delicious Pork Wellington (definitely don't look up Alton Brown's recipe for it). And certainly don't let anyone know that if you put it in a sous vide with a little olive oil in the bag, it comes out as one of the juciest, most tender cuts of meat you've ever eaten in your life, for less than the price of the cheapest, toughest shoe-leather steaks they sell at the grocery store. Everyone is sleeping on this incredible cut of meat, and I would very much like to keep it that way.