With formula, you just feed on demand, same as BF. The only difference is you feed formula. So whenever you would normally feed her, yes, I'd move in the direction of slowly incorporating more and more formula feeds in place of breastfeeds. Which ones you choose to do doesn't really matter, but your nighttime feeds are key for producing your supply for the next day (they are also a heck of a lot easier to offer from the breast, rather than to get up and make a bottle). So if you want to keep some BF going, I would switch out the night feeds last. We started to move to formula around 6 weeks. It wasn't really by choice, but because my daughter couldn't latch well enough to feed enough and then I developed an allergic reaction on my breasts so had to switch to expressing. But the added formula, meant she fed less regularly and I only woke during the night to pump when she woke for a feed, so my supply tanked and dried up by 10 weeks. If you don't really mind and you want your supply to dry up, replacing those night feeds might be one way to encourage it. It might just also be about what's comfortable for you. If you feel engorged, you might need to feed at certain times just to feel more comfortable.
Otherwise, really there is no one right way to do it. I would move slowly as you're doing to give her tummy time to adjust if you are able to continue BF some. But there is no need to devise a schedule just because your FF. It will happen in time that you see a pattern develop and she'll want to feed roughly around the same times each day, but just keep feeding on demand. If she's still waking for a feed every 1.5-2 hours at night, I would continue to feed her as normal, whether it's breast or formula is up to you. The combination of getting older and moving to formula will mean she will likely start to sleep longer stretches at night, and have a more set number of overnight feeds (though the times may still vary a lot). By 8 weeks, my daughter was having maybe 3 night feeds (roughly 10pm, 1am, 4am, give or take an hour), so we would pre-make those bottles in the evening and refridgerate, then warm when she woke. So the times might vary, but I could plan ahead for how much I'd need.