I think I understand what your asking as I too would like something like this. The paypal gateway plugin (to my knowledge) only allows 1 merchant ID. So, if you are wanting multiple paypal accounts to work with this plugin, it will not work since only 1 merchant ID can be used.
I almost started a topic on this subject, but came across this one and glad I did. I'm sure some custom code modifications to the paypal gateway plugin would make what you and I want, I just wouldn't know how to do it.
All in all, if you want to have multiple users paypal accounts (merchant ID's) to be used along side the paypal gateway plugin - it won't work as of right now. And I'm not sure if they will change that. Only 1 merchant ID can be used with this gateway. You still have the option to distribute whatever amount to those you want to distribute money to, but you will have to do it manually and from your account if your account is the main merchant ID being used with this paypal gateway plugin.
I can't recommend a specific "best" payment gateway plugin as it depends on your needs and preferences. However, I can guide you on activating a payment gateway on Oxwall for your fundraising plugin:
Remember, activating a Payment processing gateway involves sensitive information. Always follow the official Oxwall documentation and plugin guides for secure setup.