Without knowing the application, we don’t really know how you are using the system.
Of course the mixer would be at the beginning of the signal chain, an the powered speakers at the end of the chain. Between the mixer and the speakers would certainly be the appropriate place for the feedback destroyer.
However, the proper location for the compressor/limiter/gate may be more appropriate in the input channel rather than at the mixer output. It depends on the application (what are the inputs, what is the location, how is it used, etc.)
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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.