Hi,
Its not possible to change activation function from nnstart gui, You actually need to use fitnet or patternet function to initialise the model and then change the activation function there. Also you can decide on weight and bias initialisation in the same functions. Regarding the number of epoch, this functions generally stop training when validation loss become saturated. But this function does not provide flexibility to change the default number of epoch. If you wish to change a lot of things and define a lot of custom function to tackle you problem, I would recommend you to use deep learning framework such as trainNetwork or dlnetwork, These are more advanced and more flexible in choosing hyper parameters.
I hope this helps you,
Cheers
