Walls and Ceilings - repairing wallboard cracks

Foundation settling problem was fixed,now I have to decide how to fix the horizontal cracks in the walls just below the ceiling. The gaps in the cracks are about 1/8 inch and run along inner walls of two bedrooms and living room.Should I fill the gaps with patching plaster or maybe nail some borders to cover the gaps? Which method would be better?

I would fill completely with a good quality latex caulk, appy fiberglass tape and finish as one would normally do. You could put up moulding or a border after if you want but I wouldn't just paint. Maybe a border in the bedrooms[not for me I hate them] but not in the living room. Maybe some crown moulding, but you may have to repaint after any way. Why bother.

Questions, how is latex caulk and fiberglass tape better than using patching plaster.Also "finish as one would normally"how do you finish after using caulk and fiberglass tape?And what did you mean by"I wouldn't just paint ".And I wasn't going to both plaster and border,just one or the other.

It would be very helpful to know what your walls are made of. Are they plaster or sheetrock. If they are plaster I will not give you advice because I don't do plaster on a regular basis and would not be sure that the advice given would be right. But I do know that you shouldn't just put a border up over a crack under any circumstances IMO. I meant to say I would just paint not I wouldn't just paint. I don't know if it is appropriate for plaster "if that is what you have" you never said,but the fiberglass tape reinforces the repair making it stronger and less likely to reappear. You original post left a lot of info out that should have been included. My reply was for sheetrock repair. I picked sheetrock [my bad]. Giving advice for every possible scenario simply bacause the poster did not include important info gets old fast. I don't know how some of the people around here do it. BTW I have a car. How much will you give me for it

Should have mentioned it was sheetrock,now how would latex caulk be better than patching plaster?

more flexible and has adhesive properties among other things. It is just the way I do it. I have never had a prob with it. You could skip the caulk and fill the crack with joint cumpound but imo stay away from the plaster and use the caulk and the joint compound or the joint compound alone with the fiberglass tape.

I forgot to mention that whatever you choose to do put at least 1 drywall screw[ 2 is better ] above and below the crack at each stud. Be careful driving in the screws above the crack to make sure you do not screw up the tape at the wall ceiling joint. You could pull in the sheetrock on the wall so much that it could tear the tape embedded in the corner where the ceiling meets the wall.