NDLP is the style of holder, R is right hand, 12 is the shank size (12/16ths, or 3/4").
A quick google says that a Kennametal SM414 is in fact the carbide seat for the insert, not the insert itself.
Kennametal's website is not great at showing insert/holder compatibility, but it looks like you'd want a DPGR insert like this:
Top Notch™ Profiling - Inserts
and your holder appears to be an inch version of these:
Top Notch™ Profiling - Toolholders
The other appears to be a standard top notch holder, which should accept any of the top notch style inserts from kennametal, tool-flo, or any of the others that have ripped off the top-notch system since the patents ran out. Here are all the top notch grooving inserts from kennametal:
Kennametal(R) Grooving Inserts - Deep Grooving Tools For Sale Online