I too have often found that people tend to misremember Vader the most when it comes to OT characters (I wonder if the Marvel comics might have had something to do with this?). That’s not to say he isn’t also calm, or perhaps ‘restrained’ is a better word, in the OT, but anger was obviously an important part of what made up the dark side of the Force from very early on. The proto-Vader character of Valorum in the early drafts was actually much more PT Anakin-like in many aspects. I will however say that OT Vader was definitely more calm than he was in ROTS, which makes sense as he’s much older and more experienced later on. That’s a thing that I really liked about Charles Soule’s Vader comic is that he shows Vader gradually becoming less ROTS-like and more like the OT version throughout the series (I haven’t read the following Vader comics so I can’t comment on those). Though either era of Vader is a far cry from the unhinged rage of Kylo Ren in the ST, but I do agree that suggesting that he was always calm in the OT is blatantly misremembering what he was actually like in the OT.