Typically, the pax are asked if they would care for a drink once the safety briefing is over and they are also made aware of where their catering and location of soft drinks, coffee, booze, ect....
While inflight, if the opportunity arises, one of us might go back and ask if eveyone is comfortable and maybe update them on our ETA and confirm their transportation or if one of the pax comes forward to get a cup of coffee we'll ask if everything is OK. Other than that, they are on their own.
As far as smoking is concerned, YES, te pax can smoke inflight.....however, I have grounded a number of planes after the trip is done becasue of the smell in the cabin...especially with cigars. If the Company insists on me flying an additional pax leg with the cabin wreaking of smoking I will refuse to do it.....I have never had a problem do so.