1) Behaviours that are unchecked are completely deactivated and do no 
longer take part in the matching process (I just re-checked the 
sourcecode).

2) RB uses only the identifiers, not the names of Behaviours to 
identify them.

3) You really shouldn't modify RB's bundle. It breaks the code signing 
applied to RB and can (and most likely will) give you problems with 
Leopard's firewall and keychain, both of which Apple has designed to 
keep apps with broken code signing out and/or repeatedly get on your 
nerves by asking the same questions over and over again on each start. 
(On the plus side - and the reason RB uses code signing - with code 
signing intact Leopard automatically handles firewall settings and 
won't prompt you for keychain access after software updates)

4) "Manually activated" means that you have to manually activate the 
Behaviour in order for the Behaviour selection to stay "sticky" until 
you manually deactivate it. This can be achieved by either

a) mapping an action found under "Behaviours > Behaviour" in the 
Mapping table 
b) using an action found under "Actions > Behaviour" in the Menu table 
c) using the menu and select a "Activate XY" entry

All other ways to start an app - including outside of RB, via 
AppleScript or by dragging and dropping an application from the Finder 
into RB's menu - are not handled as "manual activation".

BTW: you really shouldn't invest any time in a duplication of a 
Behaviour that RB already ships with. It's better to add custom 
actions to the existing Behaviour if you need anything in addition to 
what's already provided. That way you automatically benefit of feature 
upgrades and bugfixes and don't have to manually keep your own 
Behaviour in sync with the latest Plex updates.

Best regards, 
Felix Schwarz