"Well, you are always nice."
Translation:No, sinä olet aina mukava.
You can change the word order, but it usually changes the emphasis. The most natural or neutral word order is "no, sinä olet aina mukava".
If yiu want to give more emphasis to "aina", i.e. that the person is always nice, you can say "sinä olet mukava aina".
If you say "(kyllä) sinä aina mukava olet" or "aina sinä mukava olet", you kind of say that the other person is always at least nice, but ... there is a "but", as if you were conferming a previous statement about the person being nice but not necessarily other things said.