Hey in case of ADCs and their respective references, please verify whether the process supports trimming. If that is the case, you can get your resistors trimmed to get the accurate bandgap value. You can hence do the design to get the value in vicinity and after trim, you can get the most accurate value.
Another thing, if the value increases, there should not be no problem because, your Vin is still inside your VREF limits. The problem comes if your Vin is outside your VREF limit.