Hello. Yes FHE and differential privacy should combine very well. In particular, in Concrete ML, you can train your model with a clear dataset and differential privacy, and only use FHE to protect inferences. There are demo in our repository to use a pretrained model and compile it to FHE. Eg, look at Tree-based models | Concrete ML
The training with differential privacy is not modified so not impact to expect here. And then the FHE part is also independant of how the model was trained.