my experience with bike packing v panniers is that the heavy stuff goes in your frame bag as near the bb as possible, the lighter and bulkier stuff goes under the saddle or bars.
i remember having a loaded bike with panniers and its fine for road stuff but you get the wobblies and handling is awful off road. a loaded rack also feels disconnected from the bike.
ive spend several days with my bike fully ‘bike packed’ and although the bike is naturally way heavier, the way the weight is distributed actually make the bike feel really good even in full off road settings. and as others have said, with the soft packs and compression straps, it makes the load as small aa possible.
i thought id hate my bike loaded up with modern bike bags but it think its night and day compared to racks and panniers.