You want a minimum of 8 physical splits on the drives.  In most cases you will need a lot more in DMX to use all the capacity of the disks, so just use the largest possible TDAT volume size that will use all the capacity of the disks.  Even number of physical hypers may be slightly better.

YES

2000GB

RAID 6 (14+2)

239.98

YES

2000GB

RAID 6 (6+2)

238.42

YES

2000GB

RAID 1

218.55

NO

2000GB

RAID 1

219.17

NO

2000GB

RAID 5 (3+1)

239.10

NO

2000GB

RAID 6 (6+2)

239.10

Correct, largest volume on DMX is about 60GB.

If you had a mirrored TDAT pool on 146GB drives, you would want much smaller than 60GB TDATs.  You would want something like an 18GB TDAT, which was why I mentioned the minimum of 8 physical TDAT splits or hypers per drive.

For a 600GB drive with RAID1 TDATs, you still want to go with the largest logical possible, that will be 10 splits per disk. 3+1 with 600GB drives will be about 30 splits using the largest volume possible.

For 600GB physical RAID1 TDAT, I was thinking 32GB per and 600GB physical RAID5 3+1 64GB per, approx

If I go with 65520 regardless of RAID type?

The largest hyper I can have on a DMX-4 is 64GB

what is the logic of keeping the 8 minimum physical splits on the drive?why is it so?

The DA is optimized to work with mutiple targets per drive.  In most cases the minimum number of hypers to use the capacity of the drive will be a LOT more than 8, so in most cases you won't need to worry about going below that.