I stopped using chili powder years ago. Pure heat is kind of boring and stomps out other flavours.
I had been using a few red thai peppers but these are super hot, not a great afterglow and the heat is a bit searing. Also, the capsicum ends up all over me, even if I wash my hands it's on my arms or something and gets in my eyes, on my lips. The oily stuff seems to spray about when you cut them up. So I stopped using them.
Then I went to ghost pepper
sauce which is really nice in milder doses. When it's not all about the kill from the heat, ghost pepper is nice. But it gives me vivid, silly dreams so I stopped using it.
Lately I am using around 4 jalepenos, split with seeds removed. This add nice flavour and mild zing.
I notice Frank's RedHot Cayenne Pepper Sauce is fantastic, adding only a small amount 1tsp to 1tbl really brings out the other pepper's flavours.
If you add even a little cold water while cooking hot chili con carne, I find it's ruined- so I have a rule to "never temperature shock chili". Not sure why but it's a consistent finding of mine. I think adding cold veggies can do it too.
A bit more research and I find cooking with hot peppers, they appear to be sensitive to pH.
A secret ingredient is adding vinegar which I think keeps it acidic. I have not tried lime for that.