```python
def hex_groups(values: list, width: int) -> str:
    if not isinstance(values, list):
        raise ValueError("Input must be a list")
    if not all(isinstance(v, int) and 0 <= v <= 255 for v in values):
        raise ValueError("All values must be integers between 0 and 255")
    if not isinstance(width, int) or width <= 0:
        raise ValueError("Width must be a positive integer")
    
    groups = [values[i:i + width] for i in range(0, len(values), width)]
    return ' '.join([format(group[0], '02x') + format(group[1], '02x') for group in groups])
```