So glad to see you venture into IEM reviews!
One thing worth considering to some degree, even though it can make IEMs a bit complicated to review, is the fit and the effect of the eartips - which it's good to see you talking about to an extent already. I have quite a few IEMs and I also have about 30 different types of aftermarket eartips, the reason being that I prefer to tune each pair of IEMs with the best tips rather than use an EQ, both for fit reasons, but also because I change what devices I plug my IEMs into a lot (and change what IEM I am using pretty frequently) so try to get the best sound out of each without an EQ. The ear tip material affects fit and sound: thin silicone, thick silicone, mixed materials (pliant silicone, stiffer silicone, thermally reactive polymer, hybrid foam/silicone, dense foam, soft foam). Also the bore (diameter of the opening), shape of the opening (cylindrical, horn shaped, etc.) and depth (which can affect the resonant frequency and shift it up or down the spectrum). An IEM reviewer can't be expected to test an IEM with every possible tip, that's just not practical! But it might be worth including a couple other tips regularly as alternative reference points in reviews to try and figure out what an IEM is capable of in case the included tips just weren't that great, or to ascertain what impact the stock eartips have on the capabilities of the IEM. At the very least some commentary on what the stock tips are like to try to give the reader an idea of how well they work out of the box vs. how well they might work with aftermarket tips would be helpful I think.
Also consider that personal experiences with IEMs will vary more because they bypass a lot more of the external structures of the ear and ideally they compensate for that with their acoustic performance in way that works for the individual listener. Over-ear headphones include the listener's outer ear as part of the acoustic equation (bypassing just most of the head and torso), so personal experience variation tends to be less variable - though wearing glasses can significantly affect pad seal and create a big variation for over-ear. In-ear does eliminate glasses breaking the seal, but whether the tips seal well or not or whether things like any vents in the body of the IEM are pressed up against the skin of the ear so they get partially sealed (which can vary with the fit on each person, which can be affected by the tips as well as the outer structure of the ear) will change how the bass sounds in an IEM. Also there are aftermarket eartips which are designed to do things like enhance the bass (typically by making the stem out of a thicker silicone) and decrease the treble (which can be done by reducing the bore size, i.e. inner diameter, as well as other designs). Physical changes to the eartip can affect the stereo presentation and what kind of a sound field you get, which makes them more complicated than an EQ. I also think that some sub-bass experience with IEMs is tactile and that if an IEM is producing sub-bass the type of tip and seal it has can have an impact on that tactile sensation that is not just acoustic. For all those reasons I think EQ is not a 1:1 substitute for and cannot simulate all that different eartips do.
I hope some of these thoughts and observations are helpful.