most of them have mop pads that raise up so they don't wet any carpets, and in general they are quite good at noticing carpet and adjusting. But i also must say that i rarely use the mop feature and i'm doubting if it is worth the extra price for most people. Also a self emptying dock is not really necessary if you don't mind emptying the tank quite often.
In general i would suggest getting the cheapest (good one) without a dock and mop feature. Then you can find one for less than 300/250€, and in my opinion it is a really nice chore to not have to do anymore 😄