I would not use custom forward methods, as these would skip hooks (the same would happen if you manually call model.forward(x) instead of model(x)).
E.g. this code uses forward_pre_hooks to copy to lower precision and could easily break.
Also, here the self.module is called, which will internally call into __call__ and then forward. Using your custom forward methods would break this again.
However, it should be possible to call your custom forward methods from the actual forward method in case this would keep your code cleaner.