build woocommerce wordpress site with flatsome theme

I need a website for my retail vape shop. I have a domain from GoDaddy and am hosted through Host Gator. What I need is a clean modern homepage, menus (shown on all product pages), and a product page, with a few featured products. The theme must look modern and be responsive across various platforms. I currently have Flatsome through woocommerce. Most importantly, I will need to move this site, when complete, to my current domain and hosting. The reason I have two domains/hosting is that I have a simple basic site up at my primary domain/hosting for SEO purposes which allows potential customers to find our retail store. When the site is done I need to move it all to replace the domain that is currently used for our business. I think I just need WP import/export to do this, but I'm not sure. I will have around 400 products listed and the site will be linked to my POS(point of sale) system for inventory updating, photos and descriptions. The descriptions can be in the site or stored on our POS linked as CSV files; whichever is easier. Most of the products are matrix style having multiple options of different ingredients, sizes and colors; therefore, this needs to be supported. You do not need to worry about the linking between the POS and product page - just the layout of the pages themselves. The site needs to be lightweight enough to be viewed and loaded quickly while also having many photos (most are 100kb or less but can be made smaller if needed). You will have the freedom to use whichever add-ons are necessary. I would like a search bar that while typing can guess what products you are looking for, similar to doing a google search. The checkout cart will be handled with our retail merchant services provider, but I would also like to accept paypal which our merchant services provider does NOT handle. One final point is that I would like to be able to continually update .php, mysql, and theme when updates are available. I think this is called a "child" in relation to flatsome being the "parent"? If you have questions please do not hesitate to ask. I will try and update this listing with answers to common questions as much as possible. While learning about what freelancer.com has to offer I noticed a site designed by World515 ([login to view URL]) and like how it is all setup. Something similar would be nice, but with more room for words on all pages for SEO purposes. Thank you for your time and consideration.