I’ve added both coffee and vanilla to my beer. However, not in the same brew. When I add coffee, I use whole beans in a muslin bag during the boil. This method adds a wonderful coffee background to my porter without adding any additional water, i.e. cold brew.
On the other hand, I’ve struggled with vanilla. I’ve tried adding vanilla beans to the boil, or to the secondary, or both with very limited success. I’ve even gone as far as spending $25 on 5 Madagascar beans, split them, soaked them in vodka and added them to the secondary. They added a wonderful flavor....for about 3 weeks. So, I’m curious how your method works out.