I have also purchased pixels from Etop (and other vendors). You mentioned a very large order just be mindful of potential import duty’s and taxes and if your prepared to wait 6 to 8 weeks you may want to ask about boat shipping which would be considerably cheaper than air shipping.
The other option you have is to make a smaller purchase of say 500 pixels as a sample and see if you like the quality etc.
Don’t also forget about ordering pigtails etc and if you already know which props you are going to make consider ordering custom count strings to suit these props.
I bought 3000 12v pixels from Paul and Tom earlier this year. Emailed directly for best price, chose shipping via boat (slow but cheap) and paid via PayPal friends and family. Tom was fantastic to work with, and had no qualms using the friends and family (no insurance if not delivered) based on their years of interactions with this forum and the xlights community.