"The Host" establishes that a Trill host can look like just about anything: we see two ridge-faced individuals, but also one beard-faced fellah from the species H.sapiens. DS9 is simply consistent with that, by introducing another new look among the many.
As for a "balanced" joining, I don't really see signs of that in DS9. The slug just plain takes over and has fun with the host body. At most, Dax sometimes bothers with using the name of the host. Perhaps Odan did that on weekends, too?
And "transporters harming" was bullshit from the get-go. Odan just didn't want a transporter operator using his parasite filter and exposing Odan's secret that way. Odan and Dax alike could beam safely by informing the transporter operator beforehand - and would die alike if failing to inform him.
There aren't different sorts of Trill. There is just one sort, the ugly slug. The rest is mere decoration and subterfuge. Sometimes the slugs take ridgeheaded or bearded hosts, but generally they prefer the Lexus of humanoids, the spotted Kriosian species (many individuals of which live on planet Trill and are considered Trill by citizenship, regardless of their species). And they blatantly lie to their hosts about how crucial the various parameters are for a proper match, so that they could keep on choosing as they please.