Great question — answering as the UphillTech team:
I would go with the bag they recommend. It's much easier to cool down than to warm up. You state a "multi day hiking and backpacking trip". I have been caught out with an inadequate bag, and for a single night it was manageable, but I was able to change my plans. What will you do after the first possibly miserable and sleepless night? All you will have is what you carry.
Full answer by Weather Vane: https://outdoors.stackexchange.com/a/29567 (CC BY-SA 4.0).
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