2.8, how to automaticaly merge overlapping vertices there used to be a button for this, It looked like two arrows pointing towards each other i believe. It made it very easy to snap one vertex onto another. It was located where the snaping and pivot point options are but I can't find it in 2.8 :(
nvm, found it. It's under mesh options all the way to the topmost corner of the window. :) It's called AutoMerge editing