Simon Soundman
Actually, the characters name is Simon Soundman, not sam the Soundman. and yes, I think they are the same puppet. many humanoid muppets on Sesame Street were used from puppets called Anything Muppets, which are basically blank-faced puppets who have facial features and clothing added to make a character. This is not only done for one-shot characters, but also regular ones. The few exceptions of humanoid muppets who are not made from Anything Muppets are Ernie (i think.... there have been some orange characters, like the old man at the laundry mat in Elmo In Grouchland or the King in Cinderelmo, who have heads shaped like ernies head), Bert (although some of his body parts, like his nose, have come off), kingston livingston III (i think) and bruno.
You may have noticed that most muppet humans of cartain colors normally have the same head shape. all blue muppets have round heads, all green muppets have pointy heads, all orange muppets have tall heads, and so on. I think that many of the anything muppet patterns have been duplicated, since many of the same types of anything muppets have been seen in the same shot before (for example, Chris and Big Jeffy, both blue anything muppets, were seen together in the song Go, Baby, Go, and The Count and Mumford can both be seen in the same shots in crowd scenes in bot Sesame Street: 20 and still Counting and Cinderelmo). I am not sure if any characters were eventually rebuilt as a permaneant puppet.
There have also been some scenes with ore of the same type of anything muppets that were not regular characters. In the song The Ten Commandments of health, the green anything muppet was used for bot Dr. Thad and one of the background singers. There are also examples where multiple copies of the same anything muppet are used for bot regular and non-regular characters. In the song telephone Rock, the green muppet is used for Little Jerry and the Operador, while the purple one is used for Rockin' Richard and the Cop.
here is a listing of the various types of anything muppets, and which characters are used from them:
blue anything muppets: fat blue, simon soundman, proffessor hastings, ferlingetti donnizetti (has live hands, though), big jeffy, hard head henry harris, and chris.
green anything muppets: sherlock hemlock, lefty the salesman, farley, little jerry, clementine,and one of the alphabeats.
skinny lavendar anything muppets: herbert birdsfoot, rockin' richard, smart tina, polly darton, and one of the alphabeats.
fatter purple anything muppets: the count, the amazing mumford, biff, rodeo rosie, and forgetful jones.
orange anything muppets: sully, chrissy, and dr. feel.
yellow anything muppets: guy smiley, prince charming, don music, vicnent twice vincent twice (has live hands), and monty (has live hands). (note: I think that guy smily might be a permaneant puppet, with facial features added to make other characters. don music looks like he could have been guy smiley with a wig and glasses, although don and guy have both been seen togetehr before. I have seen some bald muppets from this anythiing muppet design, but those ones had live hands).
small muppets: there are many small ones, that are usually pink, purple, and orange. these are used for characters such as rosevelt franklin, prarie dawn, andbetty lou.
Finally, to answer your other question, yes, they both appeared as grovers customers. fat Blue was a regular customer, and Sion Soundman appeared as a customer once.