While it is possible to get all the main quest line and civil war quest achievements without any issues, you have to be aware of a possible conflict which may cause you to miss the 'War Hero' Achievement/Trophy.
According to the trophy guide here it is possible to miss the trophy if you haven't finished the civil war quest line before getting in too far into the main quest line. In the main quest line 'Season Unending' you have to negotiate a peace treaty between the 2 factions. During the course of these negotiations you have to make sure that the 2 forts (Sungard and Greenwall) either end up with different factions or they both end up with the faction you are not planning on being aligned with.
A bit confusing I know. And to add more frustration to this situation, according the uesp wiki the 'Season Unending' quest has a number of bugs. So if you want all the achievements for sure, I strongly recommend finishing the Civil war quest line before the main quest line. This way you never have to go though the peace treaty negotiations and will have already acquired the 'War Hero' achievement.
Side note: Also, take a look at the miss-able achievement 'Oblivion Walker' at the link above.