London Heathrow terminals shuttle pls!?

Hi I am going to arrive on Terminal 4 of LHR. However my friends insist that I meet them on T1. I read on LHR website that this is connected by the free 'Heathrow Connect'. My questions are: - Am I allowed to take luggage (I have 2 med-size and 1 cabin-size) to the train? Are there any luggage restrictions? - Travel time from T4 to T1? - Where do I board this train after taking my luggage? Thank you in advance!