Models.features , model.encoder, and model.decoder

I see a lot of examples using model.features

torchvision.models.vgg16(pretrained=pretrained).features

so, can we use model.encoder or model.decoder too? or it depends on the architecture of the model? where can we found the documentation of them?

It depends on the architecture of the model and you can check the internal modules in the model definition.
E.g. torchvision.models are implemented here.