80-20 or 80-10-10 for training machine learning models?
1) In 80-10-10 scheme, 80% is for training, 10% is for validation and 10% is for testing. Validation set required to search for the optimal hyperparameters.

For models having no hyperparameters, it doesn't do much good to use a validation set (although, it is still useful in determining when to stop the training of the model using early stop). In such situation, one might just keep 80% as training set and 20% as testing set.

2) Yes, K fold CV can be used with simple split.