I think its fair to make the argument Harper won't sign with Atlanta but I don't think its right to dismiss the possibility. It fits - Especially a front loaded contract with a player option after the third year.
The three premium free agents are all great fits for the Braves needs: Harper, Machado, Kershaw.
Harper is probably the best fit with the least amount of risk.
Machado is similar to Harper, but not quite as good a fit.
Kershaw is probably the guy with the most potential to turn them into a true contender, but carries the most risk.
Beyond those three, I'd argue the free agent market isn't very attractive. There are a lot of aging guys who could help you, but given how everyone geared up for this offseason, there is likely to be a lot of money needing to be spent and I'm thinking it will not be a year for bargains.
With all that said, every team in baseball can see plain enough that Harper is an MVP candidate who will start his new contract at Age 26 and know how rare that is on the market. Someone is going to give him the moon and it is sort of hard to see Atlanta being that someone.
Someone will overpay for the best pitcher in baseball and it's hard to see Atlanta being that someone.
Machado might be comparatively cheap except there are big players with needs on that side of the infield, like the Yankees, who do not necessarily need to be in the Harper sweepstakes.
as much as I'd like to see the Braves make a splash, it seems like they are most likely to end up on the lower end of the free agent market.