Only the open plan area got the skim coat of plaster, that was due to its height and it would have taken me forever to tape and joint all on my own. All other rooms are getting tape and joint by me then painted. When I have taped and properly completed all the jointing and sanding stages I think it’s as good a finish as the skim plaster. Not every one will agree with that but I believe in Scotland it’s mostly tape and joint and in other countries particularly Canada that’s pretty much all they do. It’s definitely won’t change the airtightness as we are ICF so our biggest airtight challenges are the eves, service penetrations, doors and windows.