I went with this storage setup on the M4 Mini. 4" TB cable to TB enclosure with a 1TB drive and some double sided tape. Got the internal storage usage down to about 140GB by disabling Messages in iCloud, TimeMachine, clearing up a bunch of unused simulators and moving Music/Photos to the external drive. Pretty good other than increasing power usage by a couple watts.
Another bit of space saving.
GarageBand: gets installed automatically, easy enough to nuke from /Applications but that still leaves 2GB of left over junk in /Library/Application Support in the GarageBand and Logic folders.
I think its /System/Library/AssetsV2/com_apple_MobileAsset_UAF_FM_GenerativeModels. My M1 MBP doesn't have anything in this directory, but all my other machines do…