Compare two whole HDD's contents, sector-level

Question

While analysing two 4TB HDDs, which were in some kind of RAID 1 configuration, and thus have the same contents in terms of files / folders (they have been reformatted but R-Studio lists the same file tree for the main partition in both drives), I found out comparing them side-by-side with WinHex that there were small discrepancies at the sector level (and in R-Studio there are a few differences in the “Extra found files” category, which lists files detected with the “raw carving” method, based on known file signatures – I haven't yet extracted those files so I don't know if they are valid / significant). It may be slack data from former partitions.

As an attempt to figure out what these discrepancies are, I wanted to thoroughly compare those drives, to locate all non-matching areas and then quicky check them. But the comparison function in WinHex is not convenient for that purpose : one has to create a “report” file for each comparison operation, which lists every single different byte, so it can become huge if there are lots of differences, and it's not practical to quickly identify matching / different areas ; or if a limit is set, for instance “Discontinue comparison after 1000 differences”, the same tedious operation has to be done again manually each time that limit is reached, so it can be tremendously painstaking if there are many different areas throughout the files / drives to compare.

I thought that I could do this with HexWorkshop, which has a much more convenient comparison module, doing a whole scan and listing all the matching and different areas in one operation, and then allowing to directly access the begining of each listed area ; but it recognizes those two 4TB drives as “1678.02 GB” (I also have a 8TB drive connected at the moment which is recognized as 1308.04 GB, and a 3TB drive which is recognized as “746.52 GB”). It's a 64 bits version so it shouldn't have issues accessing storage devices with a capacity beyond 2TB, right ? And if I open either of those 4TB drives, only the first sector is displayed (same if I open the 8TB or the 3TB drive – actually even for a 2TB drive, which is recognized with its correct capacity, only the first sector appears).
Are these known issues with HexWorkshop ? Is there a workaround ? (The only one I can think of is to extract chunks of 10-50GB from both drives as files, in WinHex, and then use HexWorkshop to compare those files, but that's way more hassle than necessary.)