```python
def format_bits(value: int, width: int) -> str:
    """Render value as unsigned binary in exactly width bits."""
    if not isinstance(value, int) or value < 0:
        raise ValueError("Value must be a non-negative integer.")
    
    if not isinstance(width, int) or width % 4 != 0 or width > 32:
        raise ValueError("Width must be a positive multiple of four not exceeding 32.")
    
    if value >= (1 << width):
        raise ValueError("Value does not fit in the specified width bits.")
    
    binary_str = f"{value:0{width}b}"
    return ' '.join(binary_str[i:i+4] for i in range(0, len(binary_str), 4))
```