For SBs these are always foreign.  Whenever they want Whatsapp or Telegram they are not in the US and it's a scam.  I usually just block them unless I want to report them, meaning I need a message from them asking for money.

Telegram is a social media app similar to IG or snapchat.  It allows posters to send direct messages to one or more people, set up a "channel" where others can subscribe (like IG), and is based on a phone number or email for account ownership. It can be easily accessed from different devices, so if a user loses their phone, they do not lose the account. This is different than the Line App (another popular comms app in Asia) which is locked to a specific device and requires several steps to transfer to a new phone. It looks like nudity or sexual content on Telegram is not allowed in general, but I have seen "channels" that post nudity and full out porn. Maybe this is country based, or perhaps the user must complete some vetting process?  

 
Telegram is used primarily (but not exclusively) all over Asia, alongside WhatsApp and Line.  I have several "friends" on Telegram that I met while on travel in Asia. Telegram also appears to be one more place where OF creators can post thirst traps to lure new users to sign up for their OF page. Just like they do on IG and even YouTube.  

 
As noted, when I get some random message on Telegram it is invariably a scammer. But I'm still in contact though Telegram with 4 SB's/Pro's I've met in Southeast Asia.  If you frequent any US-based Asian providers, say at an AMP or similar, you may find they use Telegram to advertise. Other than that, it's not what I consider an essential comms tool for mongering in the US.  

 
Life is good

 
The Cat

In my experience if any POT even mentions Telegram it's a sure-fire scam. I've followed up on quite a few of these and they have been scammers. Now if they do it I just next them. My experiences with WhatsApp have been pretty much the same thing. Not worth it for me to have one more app on my phone I have to monitor that gives scammers one more tool to waste my time. These are all overseas scammers or scammer networks.  

Can the interactions on telegram or WhatsApp be recorded and potentially used against you?  I use a Google
Number for text messaging with POTs, but I’ve been leary of any other messaging systems

Telegram is a completely legit messaging app that I've used with local SBs in the US. The advantage is you can create a user name without linking to your phone number. Signal now allows this and Google Voice is another good option. I can't comment on the quality of encryption of these, but assume that if authorities want to find you they will.  
As far as the "channels" that's a different story. It's more likely to be some kind of "content" for sale, so would be skeptical about that.