Btrfs raid 10 pool, understand the true redundancy before failure

I understand how traditional raid and all zfs combination works.

What i dont understand is with btrfs on unraid how many drives can you lose with raid 10. With btrfs on unraid, you can mix and match sizes of drives because storage is handled at a block/chunk level rather than locking everything to the size of the smallest drive. Additional drives are not locked to each other like a traditional mirror.

So if you have 6 1 tb drives in a raid 10 (btrfs) can you lose any 3 drives and still operate?

If you had 2x 2tb and 4x 1tb for a total of 8tb can you lose up to 50% capacity without a pool failure? (1x2& 2x1TB drives or 4x 1TB drives or 2x 2tb drives)