columns-column_props.php

<?php
function lean_column_props( string $block_content, array $block ) : string {
	$width     = $block['attrs']['width'] ?? false;
	$class_pos = strpos( $block_content, 'wp-block-column' );

	$column_class  = 'w-full px-1';
	$column_class .= ( $width ? ' md:w-' . round( 12 * $width / 100 ) . '/12 ' : '' );

	// Add to the existing classes if there are some already.
	$class_pos = strpos( $block_content, 'class="' );
	if ( false !== $class_pos && $class_pos < strpos( $block_content, '>' ) ) {
		return substr_replace( $block_content, 'class="' . $column_class . ' ', $class_pos, 7 );
	}

	// Or add a class property if one does not exist already.
	$close_pos = strpos( $block_content, '>' );
	if ( false !== $close_pos ) {
		return substr_replace( $block_content, ' class="' . $column_class . '">', $close_pos, 1 );
	}

	return $block_content;
}

columns-columns_props.php

<?php
function lean_columns_props( string $block_content, array $block ) : string {
	$columns_class = "md:flex -mx-1";

	// Add to the existing classes if there are some already.
	$class_pos = strpos( $block_content, 'class="' );
	if ( false !== $class_pos && $class_pos < strpos( $block_content, '>' ) ) {
		return substr_replace( $block_content, 'class="' . $columns_class . ' ', $class_pos, 7 );
	}

	// Or add a class property if one does not exist already.
	$close_pos = strpos( $block_content, '>' );
	if ( false !== $close_pos ) {
		return substr_replace( $block_content, ' class="' . $columns_class . '">', $close_pos, 1 );
	}

	return $block_content;
}

columns-render_block.php

<?php
add_filter(
	'render_block',
	function( string $block_content, array $block ) {
		if ( 'core/columns' === $block['blockName'] ) {
			$block_content = lean_columns_props( $block_content, $block );
		}

		if ( 'core/column' === $block['blockName'] ) {
			$block_content = lean_column_props( $block_content, $block );
		}

		return $block_content;
	},
	10,
	3
);