Sort of, the RAM modules overheating is a thing, but I’m not sure that’s necessarily the problem you’re having. At any of those temperatures you should be well under plastic things melting unless there is a weird sticker on the components or piece of plastic touching something it shouldn’t. It’s a bit annoying, but if the smell is easily distinguishable, I’d just run the machine hard and then quickly disassemble it to see if you can sniff out where it’s coming from. My module sensors now hang around 70C without any issues or odors after adding thermal pads, so I’m happy to leave my altered alarm thresholds higher than 70 (somewhere between 75-85 seems reasonable).
A single RAM stick is certainly going to face more pressure on it than a dual stick configuration, so that might also explain why it’s getting hot so easily with a dGPU module, and your fans are certainly not going anywhere near their top speed for the rest of the body so that would explain why it’s feeling hot to the touch.
I would start with just using some kind of fan control like Framework Control and setting a more aggressive curve after ~60 degrees; my fans are at ~1800rpm with ~45 degree sensor readings if I’m not doing anything; Playing a game on max spec should probably come with a larger fan speed.