The charity question is easy to dispense with because it's been well-studied: the poor give more of their income to charitable causes than middle class or rich people.

"Charity" for the wealthy is really nothing to do with charity. It's a social-climbing game and part of a coordinated PR/media campaign. Charity will get you into rooms with people with true wealth and power far easier than anything else you can do.

Not all UBIs are created equal. Broadly speaking, there are left-wing and right-wing forms of UBI.

The left-wing UBI is a form of wealth redistribution to reduce extreme wealth inequality. It means giving people enough to meet their needs and have a basic quality of life. This probably won't work if the rest of society remains the same. For example, consider military personnel. If you don't live in barracks you get BAH. Landlords around a base know this so will always know what to charge. Increase the BAH and the rents go up. You would likely have similar problems with UBI unless you also solve the supply of these kinds of needs as well.

The right-wing form of UBI is simply an excuse to destroy the social welfare state and social safety net. Proponents will argue it's more efficient to simply replace everything like disability pensions, food stamps, Medicaid, etc with a UBI payment and letting people twist in the wind of private sector providers for everything.

That might make sense but, for example, living with a disability makes everything more expensive and you might have few or no options for work. We also allow disabled people to get paid sub-minimum wage as yet another form of exploitation.

As another example, we allow employers to pay below a living wage them SNAP benefits, which is twofold corporate welfare. It reduces Walmart's labor costs AND they end up spending SNAP at Walmart. And then we make political decisions about what they can spend SNAP on.

So it's a likely outcome that any right-wing UBI implementation will end up deciding what you can and can't spend money on.