I haven't gotten to play as and of the Tileans, only against them, so that's what my opinions are based on, for what it's worth. Personally I don't think the Tileans really have all that much more character than the Empire's mercenaries, and their special rules tend to be kind of "bleh." However, perhaps they'll offer some unique modelling opportunities, which may be your inspiration. Anyways, here goes:
With the exception of a few pieces of equipment, the Trantios are identical to the Marienburgers.
Remasans are almost the same as Ostermark mercenaries, with the exception being that rather than always getting to reroll failed rout tests they only get it against Dark Elves and instead get a +1LD across the board for their heroes.
Miragleans are cool, if you like crossbows a lot. If you're playing Miragleans, you should probably have lots and lots of crossbows. They play very similarly to Reiklanders except their Heroes are especially shooty as well.
I don't think any of them are unbalanced in or outside of Lustria, unless possibly being underpowered. The Remasens' special rule is particularly disappointing, in my opinion, because there's likely to only be one or no Dark Elf warbands in your campaign, and the +1 LD is nice but seems like a less tangible benefit than the other two bands' benefits. However, they're also some of the coolest looking Tilean models in my opinion, and having a cool warband is equally important as having a warband that plays well, so if you really like the aesthetic then go for it. I think they're all fine, and playable. From a gaming perspecitive I would probably pick the Miragleans.