Question

I like to know how strong they are in pvp aspects of the game if thats ok to ask

At the moment, Champions and Raiders are the most favoured classes for PvP.
Sword-Champs are beast. Spear-Champs aren't that bad, due to faster aspd.
Alot of people I know say that the Champion class is the "best class to learn PvP (if you're a beginner)."

The crossbow knight fails quite badly in terms of damage, but they have amazing surviving capabilities that make up for that.
Myself i use only a crossbow knight and they do quite well against most classes.
However i advice you there's three classes you can't and shouldn't try to kill alone:
First: Champion. Their defence is far too high for your petty damage to kill, they'll pot back to health (when in wars or pvp's where pots are allowed, in self buff pvp's it can be possible, i'll continue on self buff aspect later).
Second: Other knights. You can't kill your own kind as a knight cause they have even higher defence than a champ and therefore you both will be hitting 200-300 damage, which is far from enough to kill.
Third: War support/battle clerics. Because of the heals if they gear themselves decently you can't take one down alone.

I advise going for bourgs, mages, support clerics (any cleric with a topaz 7 in the wand), artisans, scouts and raiders.
Crossbow knights have a high amount of accuracy compared to most classes and go well against raiders and scouts. The attack power is the lowest of any possible class though, and attack speed isn't that well either. Knights are more ment for supportive roles, for they have quite annoying skills with even more annoying effects.

In terms of 1v1 battles without food, the knight (sword and crossbow) is very good. The damage isn't high so expect long fights though, but cause of the defence they don't hit you much either and you probably kill them before they can kill you.

Thank u for ur replies and my late response =D and thank u jerrey for the tips really appreciate them alot