I sell physical prints mostly out of the fear of someone reselling. Like you said, they could still do that with a physical copy by scanning but at least that’s a little more of a hassle. I’d also hate to see my art printed on shitty paper or the colors are completely off because the buyer (or print service they use) doesn’t put in the effort to get the colors just right.
I took off my "printable-creator" hat and put on my "printable-marketing" hat. :) What I found was that marketing demanded as much creativity as actually creating a product, especially when you're marketing on Pinterest. My whole strategy was VERY simple and EXTREMELY effective - I set a goal to create at least one tall graphic every day presenting my Life Binder product. You might be wondering how I was able to keep coming up with ideas. Well, one cool idea I had was to take each page of the Life Binder and create a whole pinnable graphic around that one page. That alone gave me 27 pins to create. 
The second is a receipt on behalf of the Wrought Iron Range Company of St. Louis, Missouri. The company manufactured steel ranges and kitchen equipment. The receipt is made out to J. Stanley Adams & Company of Maryland, who purchased 28 pounds of grey iron on July 10, 1921 for a total cost of $14.00. A PAID stamp, dated August 12, 1921, appears on the lower half of the receipt.
So the moral of the story is that success takes time and it's all in your head. In my first 18 months on Etsy, I made less than $1000. In my second 18 months on Etsy, I made $30,000. What changed? I did. Now, looking back over this whole experience, I've taken inventory of the mindset shifts, the skills, the resources, and the knowledge that has helped me get to this point and I've created an online, self-paced course called Passive Income with Printables. It contains everything I would have LOVED to know when I started.
You can use your regular weight printer paper! Really! The idea of a printable is that it’s artwork that might be temporary or easy to switch out for something new. However, if you’ve fallen in love with one of my printables (aw, shucks!) and would like a more permanent piece of art, I recommend photo paper (matte), cardstock, premium (heavyweight) paper or archival paper. Make sure to check your printer settings and adjust the paper accordingly so it will not get stuck inside your printer. This is especially true for thicker paper.