Hey there, I used to run a Yok YZ2, they're great cars and good out of the box, my car is actually used now by a fellow Silverstone club member who loves it
only tip would be to take your time on the build and ensure that everything is smooth and well put together with threadlock used wherever screws go in to metal components (motor mount for example).
Regards to speedo I run the Orion in my buggy but the Hobbywing is also very good so either of those would work.
We're a friendly bunch at Silverstone and more than happy to help, feel free to head over on a Tuesday that suits with or without your car and we can run through any questions you may have perhaps?