Is 260 cc powerful

Such questions cannot seriously be answered. It's highly subjective. Powerful, compared to...? I never had a 260cc, but had experience with 125/350/500cc so by extrapolating:

Is it enough to get you in serious trouble if you misjudge a corner? Definitely yes.

Is it enough to propel you in Hayabusa-like 350Km/h? Hardly. You won't break any speed records on it.

Is it enough to drag you up a moderately steep incline, with a passenger and some luggage? Well... only just. Again, you won't be doing it in the third.

Is it enough to give you a momentary boost when overtaking something? Absolutely. As long as you're not already trying to go with all the 120Km/h the bike is likely capable of.

So, in short: usable - yes. powerful - naaaaw...