I found 1mm to be way too thick for the copper shim. 0.5-0.7 should be better. As for thermal interface, I’d suggest Gelid GC-Extreme or AC MX-4 (the cheapest one), those are top performers. As for the thermal pad, I used an arctic cooling one. I’d advise against buying from chinese retailers.
I can confirm. I bought only the cheapest from Aliexpress and Ebay, and it didn’t do me much good. Just invest a couple of bucks more and I am sure you will have a better experience.