Using a shared non profit is a bit like sharing a house together. It is very convenient, we can share the burden of doing the admin, but it also comes with limitations.
The All for Climate fiscal host cannot take the legal responsibility of your actions, that would put all the other collectives whenever you do something (and some of the collective are actively engaged in actions of non violent civil disobedience, such as Extinction Rebellion).
That means that all active members of your collective share the responsibility (like unions).
You cannot engage the responsibility of the fiscal host, that means that you cannot hire someone, unless you hire a freelancer for a well defined task, for a defined amount of time.
You don't have direct access to your money. There is a well defined process to claim the money (see "How to spend the money on your balance"). It can only be spent to fulfil the mission of your collective (as defined by you, and approved by the admins of your collective), with proper documentation (expense receipt or invoice) and it takes a couple of days to be paid (for the fiscal host to process all the payments).
Think of the fiscal host like someone in your community offering their garage to store material for your project. You don't have the key of the garage but you can access it following some rules set by the owner of the garage to make sure that other groups can also benefit from this storage space. The only difference is that in this case, the All for Climate fiscal host is storing money.
The goal of All for Climate is to enable unincorporated groups of people to be able to receive and spend money in a transparent way. If your group already has a legal entity, then you don't need All for Climate.
You cannot use All for Climate as a way to channel the money to another legal entity, that would be breaking the promise made to donors that expect an itemized report on how the money is spent.
That's why, we require a much hire level of scrutiny for expenses of more than €1,000. We will usually ask you to break those down to smaller pieces in the interest of transparency whenever possible.
The only exception is when you are closing down your collective. If you still have a balance, you can decide to donate it to All for Climate or to another non profit that is also acting as a fiscal host on Open Collective, or to another non profit that is pursuing the same mission as your collective.