You haven't asked for help, is it because you think you know enough? You don't know enough but at least you are here and perhaps you are looking for helping in which case you should be commended. You still have much to learn but you're at a good place to improve your skills.
No reason to do one or the other, it's possible to have both. But be careful because one could hurt the earnings of the other.
One way around it is if you have a forum topic that is very specific to a kind of product. You can then create a template style specific to that forum and modify the php file for viewing topics to include Amazon ads for specific products. A way to quickly catch low lying fruit (less work, natch) is to plow through your forum and manually turn specific product mentions into Amazon encoded links. A third way even lazier way is to do a site:search for amazon (site:example.com amazon) and add your affiliate code to the link.
Advertisers generally piss on forum traffic. Monetizing a forum is the one of the hardest forms of online marketing because of the poor conversions. So if you are not willing to put hard work on it then your forum is not going to reach its potential. Don't be so frickin lazy, it's annoying. I'm trying to slap some reality into you so you do better. Turn around and bend over. You could probably use a good kick too.