the Aldi ones I bought 4 years ago said bamboo on the packaging/marketing stuff, but actually had a significant % of cotton when the label was examined! Might account for slow drying? Fine for work or day walks when not working hard.
Bamboo is just the cellulose source - basically they are viscose - nothing new there.
After avoiding merino for years because of the itch factor (for me), I tried a Rab MeCo this autumn. works well and comfortable. Still smells after a day, but not as bad as most synthetics.
It can be rough going off-path, (ankle turning tussocky grass, uneven ground and wetness are the main issues) but it can be rough going on some marked paths too!
And, you will have to go 'cross country' a fair amount unless staying off the main high moors by using longer routes and roads.
As long as you don't over extend yourself, make sure of your fitness to cover your intended distance whilst carrying all your gear, can navigate proficiently enough and are prepared for travel in wet weather/poor visibility, then you'll be fine!
I guess you've had plenty of day walks in such terrain?