Are powers cumulative in Smallworld?
The rule you reference is correct: powers are cumulative so you can get a +2 bonus like that. Some race/power combinations are indeed much more powerful than others in Small World; a key balancing feature is that powerful options will usually be claimed higher up the list, which means you have to pay several points to claim them, while weaker options will sit around at the bottom collecting those points until they're not looking so bad anymore. Also, remember that you always need at least one token to conquer a region, so a +2 bonus does not help any more than a +1 if the region is empty.