It definitely makes a difference, there are some runelite plugins (both allowed and against the rules) which make pvp easier for those using them. I think almost all players think that the improvements to the game we get from plugins outside pvp are worth the negative aspects of their use in pvp.
There are also straight up bots people use sometimes in pvp which aren't possible for any human to fight. They can react to what you do instantly and perfectly, you can't really touch them. They're very rare though, the people who are capable of making them keep them expensive and uncommon.
I would say "players" using bots is a fairly minor problem. The overwhelming majority of the bots around are from people making money out of them. I'm not sure if many of these people really play the game.
For people who don't play the game it might be hard to understand the scale of the botting problem. Recently the majority of the top 100 accounts in the highscores for killing a boss called leviathan got banned. Its not unlikely that in the top 100 there was one real human (who went fron rank 77 to rank 14 in the highscores because so many who were ahead of him got deleted).
