X3 on Wrightsock for long days walking and hiking. They are a double sock by design but are a bit higher as a low cut ankle crew. Once you wear them you will not care.
I have hiked and backpacked for 30 years and used to use a liner sock system. Honestly, I would always have socks bunching up somewhere so I ditched these and focused on perfecting boot/shoe fit and I would advise doing the same.
The Costco merino sock (I have been buying them for years as daily wear around the house or casual boot socks) are just cheap all-purpose socks and definitely too warm for Ecuador. They last half as long as a similar Smartwool.
Darntough are indestructible, but not very comfy for my tastes. The yarns just feel rough and they seem a little lower on my calf than I prefer.
I wear Smartwool for daily wear and shorter hiking and biking days. I agree that their PHD line may be you are stylistically looking for. Plus, they dry very fast.
But on long days (especially when my feet may get wet) I reach for the Wrightsocks every time. I just bought three new pair for hiking last week. They will be going with me when we hike the TMB in July.