Is there a way in MacOS to view filesystem details, including cluster size, for an already created exFAT partition?

You can use either diskutil info ... or sudo newfs_exfat -N ... to get various (but different) details of your ExFAT file system:

1. Get the device list:

   diskutil list
   

2. Choose the partition:

   diskutil info diskXsY
   

   Example:

   user@host ~ % diskutil info disk1s2
      Device Identifier:         disk1s2
      Device Node:               /dev/disk1s2
      Whole:                     No
      Part of Whole:             disk1
   
      Volume Name:               Share
      Mounted:                   Yes
      Mount Point:               /Volumes/Share
   
      Partition Type:            Microsoft Basic Data
      File System Personality:   ExFAT
      Type (Bundle):             exfat
      Name (User Visible):       ExFAT
   
      OS Can Be Installed:       No
      Media Type:                Generic
      Protocol:                  PCI
      SMART Status:              Not Supported
      Volume UUID:               B44618D6-7DA7-35B0-BB27-C39785AA75F8
      Disk / Partition UUID:     7C734251-4E83-4537-885C-237D94F50633
      Partition Offset:          210763776 Bytes (411648 512-Byte-Device-Blocks)
   
      Disk Size:                 1.1 TB (1073530011648 Bytes) (exactly 2096738304 512-Byte-Units)
      Device Block Size:         512 Bytes
   
      Volume Total Space:        1.1 TB (1073495408640 Bytes) (exactly 2096670720 512-Byte-Units)
      Volume Used Space:         10.0 MB (9961472 Bytes) (exactly 19456 512-Byte-Units) (0.0%)
      Volume Free Space:         1.1 TB (1073485447168 Bytes) (exactly 2096651264 512-Byte-Units) (100.0%)
      Allocation Block Size:     131072 Bytes
   
      Read-Only Media:           No
      Read-Only Volume:          No
   
      Device Location:           Internal
      Removable Media:           Fixed
   
      Solid State:               Yes
      Hardware AES Support:      No
   

3. or sudo newfs_exfat -N diskXsY

   Example:

   user@host ~ % sudo newfs_exfat -N disk1s2
   Reformatting existing ExFAT volume
   Partition offset : 411648 sectors (210763776 bytes)
   Volume size      : 2096738304 sectors (1073530011648 bytes)
   Bytes per sector : 512
   Bytes per cluster: 131072
   FAT offset       : 2048 sectors (1048576 bytes)
   # FAT sectors    : 65536
   Number of FATs   : 1
   Cluster offset   : 67584 sectors (34603008 bytes)
   # Clusters       : 8190120
   Volume Serial #  : 5ea31cc5
   Bitmap start     : 2
   Bitmap file size : 1023765
   Upcase start     : 10
   Upcase file size : 5836
   Root start       : 11
   

   Hint: the message "Reformatting existing ExFAT volume" is misleading; the file system won't be altered.
   From man newfs_exfat:

   -N      Don't create a file system: just print out parameters.