guild question
The leader can set permission for any rank to queue upgrades.
There can be more than one leader.
The others I do not know. Have not bothered using any banners yet.
If it says in the description allies, then everyone can use it. 
Example, I’ve seen guilds dropping defense banners during major DEs. I also benefit from it as long as I enter the area of the banner. I can even pick-up the banner and move it elsewhere or use it as a weapon.