We got the cart before the horse and are currently still using a Windows 7 computer & purchased the latest EW subscription. Can we backtrack so we can use EW w/out the watermark? 

I'm not an EW employee, but build 7.1.4.2 was the last version that would run on Windows 7. As far as I know your subscription should allow you to register that release and use it without the Watermark. You won't have all of the latest features like the alternate output and it's stuck with using Internet Explorer for the Web which can cause some issues with certain websites. You have to click on the notice about the unsupported browser that you understand (or something worded similar to that) to be able to access Song Select, but you will be able to use it.

You might want to contact them by telephone (+1-918-250-1493) during regular business hours, Mon thru Friday 9 AM - 6 PM CST,  or go to the support page (link below) and open a Support Ticket to find out for sure.

You can download build 7.1.4.2 from the regular EW7 download page. You have scroll down a bit to get to the link for it.

https://support.easyworship.com/support/solutions/articles/24000018839