Most stomp boxes (with the exception of Expression pedal inputs [rare], Effect loops [also rare], and Stereo plugs) are TS only, Moog included.
But the MoogerFoogers, as you know have plenty of the Expression Pedal inputs and some have Effect loops also known as “Insert” cable points (such as the Delay and the new ClusterFlux).
From an expression pedal perspective, Moog will accept a TRS cable for an actual pedal or a wired Potentiometer but will also accept a TS cable if the voltage is coming from either another Fooger or from a 251, Analog synth, etc.
It all has to do with whether or not the ‘sending’ device generates a voltage of it’s own. In the case of a passive expression pedal (such as the Moog pedal), Voltage from the pedal is required and that’s what the “R” is used for. Voltage is sent from the Fooger CV 1/4" jack on the ring, and returned (after attenuation) on the tip. Sleeve is merely ground.
Other Moog products such as a Voyager VX-351 or a Multipedal 201 only have TS jacks and actually SEND voltage so do not need TRS cables. This is confusing because on the MP-201 hand, it’s an expression pedal so, right? Well yes but it has a power supply and is capable of sending voltages and even different type of voltages which is handy.
From an Effect Loop Insert perspective (and Diamond Memory Lane does this also), standard ‘insert’ cables may be used; the type that a mixing board will will to take an input and route it through an outbound mono effect processor. In essence, it sends the audio signal out of one of the contacts and expects it to be received back on the other. Well, the delay fooger does the very same thing, so it requires a TRS cable on that input.
Finally, there are a few ‘special’ cases such as the RATE/STEP jack on the MF-105 MuRF pedal. It takes a TRS jack and acts as tap tempo on on one fo the contacts and a ‘step’ or gate on the other but if you read the manual or read some of the postings here you’ll see that you can insert a standard cable 1/2 way and leverage one of the functions without soldering up a special cable (else buy a step adapter from Moog).
I shoudl also mention that Stereo jacks are rarely used for Audio on these pedals; rather, the pedals that are capable of Stereo will have a Mono jack and a 2nd audio jack that can be used when Stereo is desired. Upon either pedal startup or hardwired within the jack, is logic or points to enable a Stereo function if a jack is present in the 2nd audio jack.
This is a very confusing subject but I hope I helped answer some of your questions (and have not made it any worse!!). Always use caution, especially when using Voltages (as opposed to Audio level signals); Send 5V-7 volts into the wrong jack and you can damage something (Moog pedals are quite tolerant in this area but other manufacturers may be a different story).
if you have a specific example of something you want to try and are uncertain, post here and somebody will answer, I’m sure.