While Bashir certainly felt more comfortable with his relationship to the Chief, O'Brien always had some problems admitting it to himself or anyone else.
Bashir and O'Brien in "Explorers" (Season 3)
O'Brien: "You're not an in-between kind of guy. People either love you or hate you."
Bashir: "Really?"
O'Brien: "I mean, I hated you when we first met."
Bashir: "I remember."
O'Brien: "And now..."
Bashir: "And now?"
O'Brien: "Well... Now, I don't."
Bashir: "That means a lot to me, chief, it really does."
O'Brien: "And that is from the heart! I really do... not hate you anymore."
Bashir and O'Brien in "Hippocratic Oath" (Season 4)
O'Brien: "Keiko only spends a few days at a time on the station. I'm the one living in those quarters. And if I wanna set up... a little workshop in the bedroom..."
Bashir: "You set up a workshop in the bedroom?"
O'Brien: "Yeah. I don't use it when she's visiting."
Bashir: "No, of course not."
O'Brien: "She says that I'm trying to live like a bachelor again. That I'm expressing a subconcious desire to push her out of our quarters."
Bashir: "Now, that is ridiculous! I mean, if anything, by spending your free time in the bedroom, a place you intimately associate with Keiko, you're actually expressing a desire to be closer to her, during her absence. It's quite touching, really!"
O'Brien: "Exactly! Exactly! See, you understand! Now why can't she see that? Why can't she be more like, uh..."
Bashir: "More like...?"
O'Brien: "Err, um, a man, more like a man."
Bashir: "So. You wish Keiko was a man."
That is not O'Brien struggling with being bisexual. Nowhere is there even a hint of
attraction towards Bashir. O'Brien is simply missing his bachelor days, and Bashir reminds him of it. So O'Brien gets to relive some of it with his friend. One of my favorite ongoing subplots in DS9: the darts, the holosuite adventures, the Alamo. They're buddies, no wink, no nod.
And sure, they must love each other, but there are many shades of love.
As for Garak, there was some intent to make him ambiguous, but I really don't think we ever get enough to "make the call" as it were. There are some cliche "gay" things about him: the tailoring, some of his mode of speech perhaps. But those are stereotypes. Not to get back to O'Brien, but a gay crewmember is just as likely to be found in engineering as in a tailor's shop.
O'BRIEN: "Yeah, umm Keiko...I have to run another one of those damn diagnostics."
KEIKO: "So is that what you call it?"
O'BRIEN: "What?"
(shit hits the fan)
In a way I'm glad Garak never manifested as bisexual, because the character then challenges the stereotypes. When DS9 was on, I had a phase where I liked purple shirts. That was all it took to get "gay" comments, just a certain wavelength ink on a piece of cloth. The 90's, indeed. Hey, at least it wasn't teal.