I haven't used DS-EQ. But for the others, on my system (2010 macpro 12-core 3GHz, 32G, Reaper 6):
Gullfoss: very good on CPU. I never have any audio glitches associated with CPU over-load. It has always worked smoothly with either large or small projects. I consider it mild on CPU.
Soothe 2: hungrier on CPU. The more bands, the faster those bands react and quality/oversampling have a big impact on CPU use. at 1x OS and normal quality, with a moderate number of bands and action time, it seems to be pretty good on CPU, never causing a glitch. But with more specificity of bands, faster reaction, higher OS and quality, it can really tax my system. Glad it has so many options for controlling CPU use.
Teote: Not in the OP list but often talked about here. At 1x it seems low CPU but it sounds much better at 2x or greater. at 2x it really can start to hit the CPU expecially with more band selected. So gain, like Soothe it can be tuned into your system to cause the min CPU hit but it does consume at 2x and higher. In one project I have about 4 Teotes and I have to bypass them in order to play the track in realtime (It uses all high CPU draw virtual instruments).
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