Guild Wars 2

Hey !
In my guild hall the boosters only gives us an 8% bonus. While in other guildhalls they give 10%.
Do you know why?
In the wiki they say “The percentage benefit of these enhancements increases depending on the number of enhancements that the guild has unlocked. They are stackable with other modifiers”
How to unlock these enhancements?

You are lacking some. There are 10 enhancements you can unlock, and every one adds 1% to the bonus. You might be missing the PvP and WvW ones. Check all the guildhall buildings for available enhancement unlocks, or compare the list you have with the list on wiki to see what you’re missing.

Just to be sure, only the higher ranks in the guild can use the mats to buy an upgrade right?

Someone with guild upgrade permissions (not always high-ranked) has to activate the upgrade. However, anyone can donate the necessary mats.