Just chiming in about the symbiotics of the Iroma. Pretty much the key difference is that the symbiotics are organic. Even when they're a 'device' and look mechanical, they're actually living organisms. This means that they can get past metal detectors, but it also means it needs to 'eat' so it means the host has to either give it some kind of compressed biomass, or take in more nutrients themselves to accommodate it, a literal battery wouldn't work.
As for the type you link to on your sheet, extend types attach to the signature 'entry ports' of an Iroma, making it easy to attach and detach them, as well as control them. They're similar to modular gear on a power armor. This makes them good for situational or simple equipment, but they're less precise than the barnacle type, which directly attaches into the nervous system and such via tendrils, so still removable, but would require a minor operation. The other type of external mod would be a Coralian, but they can't produce those arms so that's not really relevant.
PS: I like the looks of the character.