"Epidurals are certainly associated with longer labours and more difficult deliveries, but it isn't clear if they actually cause those issues."
Yes, it's hard to unpick.
Never the less, choosing to labour in an environment where epidurals are immediately available (ie, labour ward) does seem to result in much higher likelihood of complications in birth, even if you're a low risk, healthy woman.
OP you want to think about what your priorities are. If you can't be at peace with the thought of labouring without an epidural, you need to go to the labour ward and then work out how you feel when you get there.
If your primary wish is to increase the likelihood of having a straightforward birth, then you might want to put yourself in an environment where epidurals aren't immediately available (ie, home or birth centre).
Is that possible for you OP? Are you low risk?
Have you had a chance to debrief your first birth with a midwife? That might help!
I also think it's important to realise that when it comes to the need for pain relief the things which really make a difference as to whether you can cope are usually about how much mobility you have, whether you're induced or not, how good your midwife is, and the position of the baby, over and above anything which is intrinsically to do with your pain thresh hold. Also whether or not you have access to a pool. The only way to max your chance of using one is having a homebirth.