That is one of the problems with canned curry paste - salt. I don't put any salt in mine, as this means I can add more fish sauce, without it being too salty! Another problem is that almost all store-bought curry paste I ever tried had some flavor in it, I have never identified - at first, when I , I thought it might be shrimp paste, or one of those other ingredients I had never used, but I never could figure it out, even after using all of them I ever read about. And years later, a friend that I used to make many of those Thai dishes with, and experimented with recipes, and different brands of ingredients, moved away, and when I went to see him, he made everyone a Thai dinner, and the red Thai curry had some Mae Ploy. I wasn't going to tell him I could tell, but he brought it up, and said that he just didn't have the time to do those things anymore, and they were still better than no Thai!
Before he moved, and we were experimenting with all those Thai things, we came up with favorite recipes for curry pastes (and many other things, as well), as well as the best peppers to use in these things, and we tried a lot of things! Here is a book, that I got some of my favorite recipes to this date from, and the author explains that the readily available (in this country) Numex peppers were as close to what he used in Thailand that he could find.
Funny thing is, we tried Numex mild, hot, and very hot, and the mild had the best flavor! And something we tried, since we also cooked a lot of Mexican food, in which this is essential, was we toasted the peppers, before making a batch of curry paste, but we both agreed that the toasting didn't enhance the curry flavor - it sort of covered up other flavors, by intensifying the peppers.
One favorite Thai curry paste from that book above is titled "Classic Red Curry Paste", but it's not really classic, as I haven't seen this method used in any recipes in any other book I have. What makes it different is that the whole cloves of garlic, and the shallots, cut into big pieces, are dry cooked in a skillet, over medium heat, for 5 or 6 minutes, until softened and lightly browned. And another thing it has, that I put in many others, in addition to the 3 oz mild, numex, is 12 Thai peppers, to add heat - the kind like chile de árbol, but hotter. Some recipes in other books would have just a half cup of those peppers, so much more heat, much less flavor, and much less paste would be used in recipes, so it was obviously not nearly as good.
Another favorite paste from True Thai was the Panang Curry Paste, which had some Makrut/kefir lime leaves, ground up with everything. The yellow variety (don't recall the actual name) wasn't as complex as the others, but had 2 tb ground turmeric, and I think that one had guajillo peppers (tried those in one other recipe, but weren't as good as the numex. He also had a vegetarian version, substituting creamy peanut butter for the shrimp paste, which was good, but not the same as all that umami from the shrimp paste!
Can you tell I am obsessed yet?

Any more questions?