```python
def hex_groups(values: list, width: int) -> str:
    if not isinstance(values, list):
        raise ValueError("The first argument must be a list.")
    if not all(isinstance(byte, int) and 0 <= byte <= 255 for byte in values):
        raise ValueError("All bytes must be integers from 0 to 255.")
    if not isinstance(width, int) or width <= 0:
        raise ValueError("The second argument must be a positive integer.")

    hex_values = [f"{byte:02x}" for byte in values]
    groups = [hex_values[i:i+width] for i in range(0, len(hex_values), width)]
    return ' '.join(' '.join(group) for group in groups)
```