Questions about delegation

[Bob McDonald]

I have a DNS server that serves a zone for domain example.org.
That DNS server lives at 192.0.2.53
As part of hosting that domain, a child domain is delegated. (
gtm-int.example.org.)
There are two NS records as follows:
gtm-int.example.org. IN NS gtm-int-east.example.org.
gtm-int.example.org. IN NS gtm-int-west.example.org.
gtm-int-east.example.org. IN A 203.0.113.53
gtm-int-west.example.org. IN A 198.51.100.53
(and yes, in this case the delegated child domain lives on two F5 GTMs)

The devices hosting the delegated child domain both contain NS records
which match the parent's NS records for the child domain and they contain
glue records which also match the parent's A records for the NS records.

Here are my curiosities:

1) should the NS records for the delegated child domain be hosts which
reside in the parent domain or the delegated child domain? (or does it
matter as long as the glue is correct?)
gtm-int.example.org. IN NS gtm-int-east.example.org.
gtm-int.example.org. IN NS gtm-int-west.example.org.
gtm-int-east.example.org. IN A 203.0.113.53
gtm-int-west.example.org. IN A 198.51.100.53
-OR-
gtm-int.example.org. IN NS gtm-int-east.gtm-int.example.org
<http://gtm-int-east.example.org/>.
gtm-int.example.org. IN NS gtm-int-west.gtm-int.example.org
<http://gtm-int-west.example.org/>.
gtm-int-east.gtm-int.example.org <http://gtm-int-east.example.org/>. IN A
203.0.113.53
gtm-int-west.gtm-int.example.org <http://gtm-int-west.example.org/>. IN A
198.51.100.53

2) Do I need to specify a null forwarder statement for the parent domain?
(to prevent query forwarding to the delegated child domain)

Regards,

Bob
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