Hi - I'll try and answer your questions!
These are my first (and probably only) children so no comparison unfortunately.
You are so right in saying my head was spinning - I was also just a teeny bit high in gas and air!! I then developed a reeeeaaalllly high bp post delivery and was on all sorts of medication and not allowed to get up / was on lots of drips which was ironic as they'd not been needed for the actual birth!!
I was monitored throughout but one of the midwives was a twin mum and she was very encouraging of me just doing my own thing. So I just stayed on my knees kneeling up over the back of the bed.
I'd had severe SPD - signed off work from 24 weeks so was keen not to be on my back. But had come to accept in my head that it would probably have to be so - also as I had gestational diabetes. But they weren't worried about that - guess labour wasn't long enough!
I'd actually already had a meeting with the anaethetist re siting the epidural for my planned CS at 37 weeks due to previous back problems, the spd and allergies.
They'd put me in a hospital gown when they discovered I was already 4/5 cm because they all thought I'd be off to theatre for a CS. But as I said there were none free - so I must have been a lovely sight to all those people wandering in and out - the first thing they saw was my bum!!
They put in lines for everything - and the anaethetist was popping in and out - I think he felt a bit left out 
DT2 was only 3lb5 compared to her brother 5lb3 I rather imagined her just falling down into the empty space as she was so tiny! They did give me oxytocin to restart contractions - which is a whole other story- and the consultant had a bit of a rummage 
I think because they were premature they were keen to get her out and also avoid the cord coming first.
At our follow up appointment they told us they were actually considering prepping the delivery room for a CS - and with the obstetrician, midwives, anaethetist,pediatricians, SCBU nurses and my husband there probably couldn't have been anyone else in a theatre anyway who wasn't present in that room!!
Babies were fine - I'd had a bleed at 30 weeks and was given steroids at that point to mature their lungs so they had only to feed and grow!
Came home 3 weeks later being tube fed and trying (and sadly failing) to establish breast feeding. Although they were breast fed and topped up through their tubes with EBM and formula for 11 weeks.
Gosh this has turned into a real missive - hope some of it is helpful to you.
Glad your DT1 has turned head down - fingers crossed for a cooperative DT2 and that your delivery goes well with an understanding and supportive team 