Is it very powdery compared to other brands? My main concern is that if it's too fine and dusty then it clogs the straw. Which brand is best?

Compared to other brands, this is not "very powdery". This Taragui happens to be the number one selling brand of yerba mate in the world. It is consistent in its production, timing, and freshness as a result of its popularity. At our website we have a buying guide that talks about yerba mate type 'suave' (smooth), because the suave blend has a higher stem concentration that helps keep straw from getting clogged. Suave are 20% stems. This Taragui is 12% stems, which is called style 'traditional'. Still, dust can be a problem with any style yerba mate, and for this reason there is a technique to keep the straw from being clogged. At our ma-tea website we have the following tip: "Cover with hand, turn upside down, and shake vigorously to help prepare the yerba mate. This moves the smaller yerba mate tea leaf particles to the top in order to prevent the mate straw (bombilla) from clogging." With this technique one can drink 'sin palo' types which are less than 1% stem content. Hope this helps!

what % liif/leaves vs stem and how much caffeine/100g

The ratio is proprietary by plantation usually not more than 3% stems, the caffeine is about 1% or about 33 mg per 8 oz of infusion. More information is available at inym dot org dot ar. The National Institute of Yerba Mate. My Yerba Mate Store

What is Taragui? Translate google brings it up as eating cod

The word taragui is the name of the product in the Guarani language, it is a green tea, it is not cod to eat, I do not know where I get that information from, I hope it serves the information. Thank you

what are the instructions to brew?

According to label instructions, in spanish. Use 14 teaspoons for every 16.9 oz of water. Make sure you heat water to 167 degrees. Otherwise, it will be a bitter-tasting beverage.