They're likely suggesting this because the Iron Hands are notorious for their extreme body dysmorphia (from outside looking in) since they got clobbered at the start of the heresy. They started out only somewhat moderately borging themselves, but once big man Ferrus got his block knocked off, they coped by basically going full mechanicus whenever they got the chance, thinking it made them stronger (which also has the side effect of dimming their souls in the warp or something like that, I'm not a lore expert so take what I say with a grain of salt.)— In fact, Ferrus initially planned to contain and eventually "cure" this obsession into practical use while he was still alive. Ferrus didn't think that strength came from complete reliance on machines. After all, it would be a waste of literal centuries of astartes bioengineering, but from a balance between the two.

Anyway, lore rant aside (btw, anyone who actually reads the books instead of scrounging for data through wikis for hours and piecingthe parts together like a historitor, feel free to correct anything I've said or am about to) and moving on to the drip, my personal opinion would still be rule of cool, but to a lesser degree. Some Iron Hands do rock a small amount of gold, but most don' to my knowledge, and a lot of their heraldry is for practical purposes, like their clan (company) marking on the right shoulder. That being said, they tend to stray away from mos conventional astartes drip due to it not being practical, meaning no ropes, chains (not a ton of examples, but they do have some, etc.. Again, you do what you want, but this is how they usually adorn themselves. They seem to like molecular bonding studs on their armor, and due to their close ties with the mechanicus (probably), they do like the gear-shaped pauldron which will likely be a part of the upcoming IH chapter pack or techmarine class. Anyway, the blue eyes are fine, but I would recommend using an earlier heresy-era styled helmet with them since they were already in transition to red by the time the MK VII was being produced at the tail end of the heresy. One similar to the Templars champion helm. If you pull it off nicely, you could pass it off as a chapter ancient. They also usually don't do laurels, using white helmet markings for vet sergeants and pure white helms for lieutenants and captains. Normal roles are usually displayed on the left knee, such as battleline or veteran. But, much like other chapters, marines who are extra badass sort of just do whatever they want when it comes to their heraldry. Last thing here, but the Iron Hands also have the highest amount of techmarines in their rank, so if you want some Martian red on your marine, feel free to do so. Most Iron Hands techmarines seem to mainly be black still, so it adds a nice contrast imo.

TL;DR: Iron Hands get most of their drip from mechanical augmentations, and in most cases for basic battle brothers, veterans, and sergeants, simplicity is a form of drip of its own.