Apple messed up the PCB/config that the GPU will automatically run at 18W (full tilt) when an external monitor + internal monitor is used. The fix in the later OSes was just to lower the power limit at 15W. That 16" was a really nice laptop in form factor and physical experience (monitor, keyboard, trackpad, and especially the speakers), but the that GPU issue + Intel heat and energy profile makes it an annoying computer to use.
I've transitioned to a 16GB M1 MBA too and it's a dream. CPU temps < 60C on dev loads on a hot day (I work outside). 16GB RAM means low swap usage (I used 8GB M1 MBA before this and it was still snappy except on the very limits). Still can drive a 4k monitor or mirrored Sidecar (with BetterDummy) without a peep. Building my work project takes the same time as the i7 16" MBP without the fan noise.
I've transitioned to a 16GB M1 MBA too and it's a dream. CPU temps < 60C on dev loads on a hot day (I work outside). 16GB RAM means low swap usage (I used 8GB M1 MBA before this and it was still snappy except on the very limits). Still can drive a 4k monitor or mirrored Sidecar (with BetterDummy) without a peep. Building my work project takes the same time as the i7 16" MBP without the fan noise.