Advice on who I should romance this playthrough?

Vivienne is not a romance option anyway.

I liked Bull's romance well enough, but I played a dwarf, so I don't know what sorts of differences you'd get with a qunari Inquisitor. I think his relationship with Dorian is a bit squicky, to be honest, since Dorian seems so uncomfortable in most of the banter, so I say go for Iron Bull yourself. Just be aware that it has less content (or seems to have less content) than some of the others, though there are some really sweet moments.

Why not let your Inquisitor get to know the rest of the romance options and then see which one their personality gravitates toward, if you're having trouble deciding?

Blackwall, maybe? Bull lectured my Qunari on how she was just a tall gall with horns, and I really did not like him after that. I tried breaking lock on Solas romance, but the mod does not alter animations, so it looks silly for a Qunari female. He literally dives right into her blossom. Not sure if breaking lock on Cullen's animation would work any better, as he is taller than Solas but still Probably would miss her lips by a couple of inches. She did stand taller than Blackwall for me, but I never went so far that I saw animations & if they had to cut back on the scenes because handling the height differences was hard. He'd just felt rather boring on my first run. I was not spoiled at the time about his backstory, so... the moment I chatted with Dorian,  I rerolled into a male Qunari. That was great, just need to wear tight pants in the Keep, or D's hands clip through his hips in animations. A runaway Tevinter Altus+ outcast Qunari made for a neat couple.

I really liked IBs romance and can recommend it. Blackwall was great too. I did start Josie with one character once (I accidently deleted that playthrough)and it was nice. So basically I tried all romances available for a female Qunari (apart from Sera) and liked them. Iron Bull was my favorite though.