Yes, whichever way works for you. Why not try both and decide? I just went the simple route.
"I think" when you plug into the FX send it will automatically by-pass/cut-out the mixers built in FX. Which, if so, would be a bummer 'cause the FX is one of the main selling points of these little mixers. But, I did not read the manual. I am just going by 35+ years experience which is not always up to date with the latest technology.
I also assume that these little mixers are mostly for running sound from the stage - no sound man situation. If you have a sound man doing front of house and/or monitors then you will likely prefer to have that person make sure your house sound stays mixed for the audience and your IEMs are mixed differently for yourself, which with this mixer would give every musician the same monitor mix anyway. If that works for you then Charlie's and rockstar_not's advice works.
My suggestion allows you to hear in the IEM closer to what your audience is hearing. That means you are the FOH man, singer, musician, monitor man, etc,...


Does the noise in your head bother me ?