Do the alliance tags, for example war monger, diplomat, peace keeper and more, give any advantages..

No disadvantages, per say. It helps others (before joining) see what the alliance is focused on. Also, it helps current members to know what to expect from their alliance as well.

For a while, an alliance could be focused on peace keeping (such as more gathering than attacking others). This could be due to having a lot of low levels and wanting to not have a target on alliance back.

But then later down the line (once leveled up more) you might want to switch and join the battle for rankings.

So it has advantages in guiding others but no "perks".