I have made so many PvP builds in all the Dark Souls and Elden Ring I couldn't even count. Though I tend to enjoy lore appropriate characters with some sets of personal rules to my invasions.
The ones based off enemy mobs and NPCs I just try to engage in the same way NPC invaders do. Edgewalking, sidestepping, and just aggro and chase. My Cathedral Knight in DS3 is probably my favorite one. Aptly named Deacon and he sits in the Cathedral.
My favorite Elden Ring invader would only be allowed to do sneak backstabs and attempt parries and ripostes. No standup fights, double splody physick like its a cyanide pill if caught.
The best invasions are where the host and I double KO, followed by when I closely lose.