I bought one haute pocket one size when i was figuring out what i wanted to do when we upsized in the last couple of months. I have to say of the 4 other types of pockets/all-in-ones I bought, the haute are my least favourite. Although they are one size, Natalie can fit them without using the leg-rise poppers at all, and is almost on the last ones around the waist....so i don't think they will last as long as I had hoped. I've also found they leak more than the others (although maybe because the fit just isn't great on her)....she is 10kg now - but I bought the one size hoping they would make it to TT....and don't think that will happen!
I would definitely recommend trying a few on your baby (when your baby arrives!) before committing to a whole pack. What works on one baby doesn't work for another! Maybe a trial or rental pack? You don't want to end up with a whole heap of nappies that don't work, and having to onsell etc.
As for inserts, during the day the ones that come with the haute one size are generally ok, but you could add another microfibre or bamboo/hemp generic insert if you need more boosting.
The inserts take the longest to dry, so the microfibre ones that come with the nappies are pretty good.
Personally I would recommend happy heinys one size over the haute one size, which snazzipants also stock. Are you in Auckland - maybe a trip to the shop in Milford might be helpful?
Didn't mean to sound so negative, I'm sure there are babies for which the Haute one size are great on!