Changing Site Replication defaults

Running Windows 2003 AD, with DFL @ Windows Server 2003

I enabled Change Notification on a site link using the articles list below,
but I wanted to clarify a few things. The WindowITPro article states  

"you can make a change to the site link to enable intersite
notification-based replication by performing the following steps"

The steps appear the same in all three articles, but the MS article and
WindowsITPro article infer that the ALL replication will become intrasite
like or change based. The last article says states 3 areas will be urgently
replicated, account lockouts being one of them.

My site link is set to replicate every 15 min, but with this change I am
seeing that it takes 10 mins to replicate from one site to another, which I
take as intrasite-like to some degree (Delay for Initial Notification of an
Intrasite Replication Partner is often 300 secs and it make 2 hops). Funny
thing is the registry entry to control this interval (5 mins) does not exist
in my DC under
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NTDS\Parameters and
intra-site replication is actually instantaneous. So my DCs replicate
immediately intra-site and it takes 10 mins for the change to cross the site
link.

BUT when I lock an account out it does not replicate any faster from one
site to the next.

So this change appears to apply to all replication, making it intra-site
like though not instantaneous or urgent and it does NOT make the account
lockout replicate across site instantly.

1.      Can someone clearly clarify the effect of this change verifying it I am
accurate in my beliefs?
2.      Do I have instant replication intra-site due to the DFL being the highest
level?
3.      Lastly, how can I make all replication instant across site links (without
making it all one site as I like site affinity)? I know it can be done
because a MS guy set this at my last company during an AD Health Check.
Thanks!