Just had my twins, so here was my experience.
Birth plan. Had none. As had two elder dcs, knew the futility of having one, and to avoid the disappointment of writing one only to find that nothing happens as predicted (esp given the unpredictably of twin births). My view also (fwit) is that failure to follow a birth plan can contribute to post birth depression so better not to have one.
IV drip. Was automatically given to me, wasn't much of a choice and I was happy to follow professional guidance. It was to make post labour contracting of uterus.
Pain relief. Again, epidural was highly recommended at my labour (tho I didn't feel pressurised) and I had it. No other pain relief was mentioned and I didn't require any as with epidural felt nothing and it was ace! No adverse side effects.
Breast feeding. Not discussed. assumed that I wld make decision after labour, which I felt up to doing. Not massive amounts of support here, but had taken a twin pillow to the labour suite and felt confident to give dual feeding a try straight away (and it worked).
C section default option. Not discussed at all. Guess if they had had to do one, wld have gone along with it if medically required.
Number of people in room. Was shocked to find out that, in my hospital at least, around 10 staff are required in the room for twin labours, 2 mw, 1 anethesis, one consultant and one doctor per each baby. May be worth you checking what is the position at your hospital. Fortunately mine came so quickly there wasn't time to get everyone in so just me, dh and two midwives. However again, was happy to follow hospitals guidance here, whatever to secure safe delivery.