Easy to upgrade, maybe modular so a light supplied to light a 2x2 could be reconfigured to light a 1x4 or upgraded to light a 3x2 without it looking like a 1x2 light has been grafted to the side. This might not be easy as you are stuck with 400mm long strips. Being modular may also make them quicker and easier to build.
I wouldn't want to be poking a screwdriver into my driver to dim it unless I knew what I was doing, so a B type driver with an adjuster knob set up so minimum setting is for veg and maximum setting for flower or something like that. I could draw a diagram for that if you like.
The inrush current of these drivers are pretty high even if its only milliseconds it might be enough to weld the contacts in the relays in the sonoff.
Your website isn't the easiest to navigate, the shop at solstrips uk link at the top of the home page is easy to miss, scroll down a little then there is a banner for the US site I bet a good percentage of people visiting your site click that and go to the US site before finding the products on your site. To buy a solstrip takes 4 clicks to get to the page to choose options then add to basket. Might be better to have your product pages at the top of your homepage then at the bottom to order outside the UK click here.