I'll admit I bought that WeLightBrick set and just received it last week. It's lepin (or some other non-Lego brand bricks), but the quality seems equivalent so far. I personally have no issue with non-Lego bricks, but hate seeing an MOC designer get ripped off (they send what I'm sure is an unauthorized copy of OneCase's instructions), so I'd already bought the plans from OneCase. If it goes together well I'll probably buy the Executor brick collection from Jeremy, as he's both cheaper than WLB and very up-front that he doesn't supply instructions; he provides a link or email address for the MOC builder to purchase the instructions from.
One thing to be warned about: the WLB set substitutes the rare engine hemispheres for the cone pieces from the UCS SD kit, and the clear stand pieces for the two companion cruisers for cheaper colored pieces, along with some less critical color substitutions in the interior structure. You'll need to source those few pieces yourself.
Not even sure how to get started. I built the UCS Falcon earlier this year and loved every minute of it, hence my interest in the Monarch... I can't handle the massively studded surface of the UCS model, though I did purchase one for collection purposes (it will remain unbuilt). The Falcon was beautifully packaged by section, though, and even then it was an organizational challenge. No idea how I'm going to sort & track over 11,000 pieces that are bagged by part, not step.