Guild Wars 2

With the auto attack built into guild wars 1 & 2, I just have the two characters from different accounts start fighting. I just use the 1-8 skills for support in their fighting. I did it in guild wars 1 to assist in getting through the gate in pre-searing. As long as I keep them fighting in auto combat it works. If one falls the other uses resurrect on the other. I have a 18th level character in pre-searing that helps the other account raise the levels of its characters. I am mostly a PvE player, because I like the storyline and most people are above me in combat. Does it effect PvP, or can two accounts on the same server fight along-side and/or fight against one another?

I have two accounts. Does it matter if I have them both on one server or separate them on two servers? I have two computers, and would like the two accounts to have the characters fight along side one another. Problem is one account is already in Full population. So there may never be a chance for the two accounts to be on the same server. The server in question is Tarnished Coast. I tried in the morning but it is still full. Does it really matter in the selection of a world for my two accounts to play together?