What is the difference between NTM and such similar slang as NM?

NTM (“Not Too Much”) and NM (“Not Much) are the same and similar in meaning and usually used interchangeably to answer questions such as What’s up? or How is it going? NTM is a bit less formal and more conversational whereas NM is briefer and more common in texting and messaging applications. They are both used to show that nothing important is going on. The decision over them is based on preferences, audience, or mode of texting. Know more: NTM meaning