Hi Markwill,
if you prefer to limit the number of plugins, then may be Santu is a good option for you for selling your digital products (or normal products). It allows you to add buy now buttons to WordPress without a plug-in.
Basically all it takes is to add a simple URL such as ibuy.bz/apples anywhere you want on your website or in your blog posts or even in comments. When a buyer clicks on the link, it immediately adds the item into your shopping cart.
Have a look at the video at https://santu.com/en/blog/2013/09/18/add-shopping-cart-free-wordpress-com-blog/ which shows you how to add Santu to a WordPress blog.
Since you run your own WordPress Blog, you can also copy and paste some Javascript into any page or template to add your own pop-up or embedded Shopping cart.
You can find some examples here: https://santu.com/en/designers/#zero-programming-section or at the end of the video above (check out the image map example, where you can click on fruit in a fruit basket to see how far you can take this).
Different integration options are described in the Integrate section of the Santu dashboard.
By the way the links work anywhere, not just on WordPress. so you can also use it to sell your eBooks via Facebook, Twitter and email for example, which can help with your marketing.
We have been developing Santu for many years for users just like you, so I hope it will suit your requirements.
All the best,
??
sgk