Malaysian driftwood (have it in my tanks) is great-looking for freshwater aquaria as well. It is also self-sinking, which is what I love about it. I also love its beautiful dark brown color

I'd like to try Mopani driftwood too, but I can't find it anywhere (and I don't want to buy any driftwood online - I have to see the driftwood in person before I buy it).
Anyway, Lyndatu, to asnwer one of your questions: The driftwood prepared for aquarium use won't rot in your tank. This is because aquarium driftwood has been dried properly and rendered basically biologically inactive - it's dead and dry inside out. So - except for staining your water orange/yellow (or even brown) color and lowering your pH - there is nothing else that it can do to your water. As has been said above, if you boil, soak, and rinse it a lot before putting it in your tank, it will not stain your water or affect your pH. It should be completely safe if prepared properly.