There is not a lot of competition for the title of "best tourist accommodation in Luang Namtha", but I'm not sure that Zuela deserve their Tripadvisor annointed position.
First, the good: nice people, convivial backpacker atmosphere, central location, bike hire on site and cheap accommodation (80,000kip / room).
Next the not so good: (in chronological order) - booked over internet and asked for two rooms near each other (for our kids, youngest 9), but arrived and found the rooms in separate buildings; sheets that don't even cover the mattress; a single-sized duvet for our double bed; near total absence of water pressure; wooden walls let smoke in from the numerous smokers on the balcony; noisy environment (roosters, people), restaurant service so slow we had to give up (despite this list, I'm not high maintenance, but I think >100 minutes for a plate of pasta is a bit much).
We chose to stay elsewhere after our trek but there is a market opportunity to open a good guesthouse in LNT (tried to stay at Thoulasith, booked out days in advance, they may be the best option). Good luck!More