Do you have to (or should you) erase the board with the jumper each time you update firmware or just the first time you do it with the Arduino method?

If every thing is installed correctly you should only have to erase on the initial install.

Hey team, wanting to update my FW to the new RC that came out a few days ago, but I am stuck on how to do this... Do I do it the same way I did through XYZWare's offline method? Or update it via arduino? If the later, someone have a sticky or how to for updated if you are ALREADY on Repetier FW?

If you already on Rep firmware you will need to use Adruino. The tricky part is do you have the correct drivers installed so Adruino sees the printer as the proper type of port. I am work till 12:30 cst so I am unable to tell you right now what the port looks like in your device manager and what adruino needs to be set for. Also you need the full package to use Adruino. If the newer version of firmware you have is only the bin then you will need  to erase the board using the jumper and then use bocca and the command line. Again not at home so I cant tell you what the batch looks like for that.