These things are cumulative, not mutually exclusive. Working minimum wage on top of UBI would put someone in much better position than either one alone. Some people would choose only UBI, but most would want more than that.
In which case, UBI might increase the baseline for what is considered to be "subsistence". If all are entitled to UBI and can simultaneously earn income on top of that, then the base line cost for goods in demand increases so that all that UBI has done is ratcheted up the baseline for what is considered subsistence, i.e., a form of inflation.
