Going crazy!!!

I've heard that toddler plus newborn is less stressful than toddler plus pregnancy, can't say from personal experience though.
What I will say is that it's 100% normal for kids to become clingy and regress towards the end of your pregnancy. I'm 35 weeks now and my 3 year old literally cannot cope without me. Needs me for every bedtime, won't go into preschool without crying when I drop him off etc. You may well find that once baby comes, your toddler's behaviour improves.

Sorry, I don't want to be unpositive here as you asked for positive experiences only, but I found going from 1-2 extremely hard with a newborn, and my toddler has always been well-behaved, but that's because my newborn was a very difficult baby and cried hours on end for about 7 weeks then my toddler went through a rebellious stage. My baby is now 5 months old, and I love it. They've both amazing and have been for a while

15 months between my first two and I found it soooooo much easier doing two under two than I did pregnant with a toddler. Currently 35 weeks with baby 3 and I’ve got a 2 and 3 year old now and I love them more than anything but gosh it’s rough at the moment. They’ve never been particularly clingy but they literally just want to be attached to me at the moment, I literally do not get a second to myself during the day and it’s draining. They’ve gone from being able to play really nicely together to literally just arguing and tears constantly. I’m sore and tired and don’t have as much patience as I’d like right now so yeah very much looking forward to having baby here and getting back into a good routine x