If you can have a paying job and some of your 'welfare' on top of it, the incentive is obviously greater than if getting a paying job meant giving up all welfare.
Not at all. If the UBI is meaningfully large (there is really no point in something like $100/month), you would be able to live on it. If you can live on UBI, the incentive to find a job is less because the alternatives are MUCH more pleasant.
The carrot is slightly larger, but the stick becomes almost non-existent.
Are you comparing UBI recipients to people who get no subsidy/welfare at all? I'm not sure that's a meaningful comparison. And one can structure the UBI amount such that utility of income is still steeply increasing at the margin - or, phrased differently, such that folks will most likely want to supplement their UBI by doing some work on the side. It's a lot harder to do that if the premise is that you're "looking for work at this time" but not actually getting market income.
This thread is for asking any questions that might seem obvious, tangential, silly or what-have-you. Don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better.
Please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
To any future monthly posters of SQ threads, please remember to add the "stupid_questions" tag.