I had placenta praevia with my twins which was picked up at the 20 week scan. It was partial (i.e. half covering the cervix) and although there was a possibility that it would move, I was advised this was less likely due to the fact I had two placentas in there and less space. Plus, both placentas were posterior.
Mine did move slightly (a few mililetres away) but still within 2cms of the cervix, which is considered unstable. I also bled on an off - some light, some like a tap and had repeat visits to hospital with labour scares (the bleeding can irritate the uterus and trigger contractions). I had labour stopped with drugs at 25 weeks, 28 weeks and 31 weeks. From 30 weeks I was kept in hospital on bed rest as the bleeds were increasing in volume and frequency, which the doctors said was not a good sign. They warned me of a so-called 'catastrophic bleed' which is high-volume bleeding during which you can bleed out in 5 to 10 minutes, which could be disastrous if you were at home.
As Fruitful said, the bleeding isn't painful at all. The only sensation for me was of falling water, as if I was peeing myself. Some bleeds were very shortlived and slight but some were pretty big. My final bleed at 35 weeks was like a tap, although it stopped quite quickly. I was then given an emergency section.
I would have LOVED to swerve a c section but the threat of bleeding due to an unstable placenta was just too high. It wasn't worth the risk and the doctors gave me dire warnings about complications. Your consultant will be able to advise you of the best route for you, depending on whether your placenta moves and I'd go with their advice as they really do know best in this instance. If you don't have any bleeding and your placenta shifts away they may well 'allow' vaginal delivery, although you would probably be heavily monitored during delivery and they may well insist on a canula being sited in case they urgently need to access a vein to adminster drugs/blood.
NOt everyone bleeds. I know someone pregnant at the same time as me (also with twins) who had total praevia. The placenta didn't move but she had no bleeds, in spite of being warned that she was almost certain to. And yet I, with my partial praevia, bled non stop. All very random and proof that they 'worse' praevia doesn't necessarily mean bleeding is certain. It's just a lot more likely and you should be prepared for that.
So my best tip is to be prepared for a bleed. There's nothing to say you'll have one, but it's best to be prepared. Have a bag packed - enough for a stay in hospital for a few nights (mine had nightdress, cardigan, flip flops, small bag of mini toiletries, book, etc.) - and carry your hospital notes with you and a fully charged mobile. With one of my bleeds that triggered labour I was at home in bed and being able to just grab my bag and head to the hospital saved us valuable time - they were able to get the labour-stopping drugs into me sooner rather than later and they worked. Equally, try and be within fifteen minutes of your hospital so no long and always have access to a telephone.
It's not much fun as it does make things quite restrictive and it's no fun having the threat of bleeding/hospital stays hanging over you. But the good news is that it has been picked up and you will get an excellent level of care, which is always good in pregnancy.
Good luck. I shall keep my fingers crossed that your placenta moves.