I designed mine on Canva based on designs I loved on Etsy (but needed to change up to work for us) and then printed them at Catprint on 5"x7" plain heavy cardstock. Super affordable, they sent me a free proof too! I got my envelopes from Paper Source and a return address stamp off Etsy and still spent less than 50% of what it would have cost me (for our small guest list) to go through Minted or something similar! Printing directly through Canva made me nervous, as I couldn't feel the paper samples beforehand.
I designed and printed mine through Canva. I opted for the deluxe paper so it was a little thicker and a few dollars more than their default card paper. I'm happy with the quality, for me it was convenient to get it all done with the same company, they let you add envelopes too. I printed a test copy on my home printer before ordering to make sure everything was centered the way I want and had my FH and mom look it over for any possible typos, the thing with diy is you're responsible for any errors 😅
Here's mine printed by Canva as a reference for print quality