Printing through online print shops is a great way to get quality prints at a low price. Turn around times are usually pretty good so if you can wait a few days for printing and then a few more days for shipping this is a great option.
What file type to use
You will generally want to download the JPEG format to use for online print shops. They'll usually want bleed so be sure to check that option as well.
The print quality will vary between online print shops but you shouldn't have any issues anywhere. Card stock will be the thing you'll want to look at closely for final quality and feel. Most online print shops will request a 300 dpi file. That's not a problem because any PDF or JPEG from Templett is 300 dpi.
We always recommend going with 100lb card stock or greater if you can. This generally applies to cards or anything people will be holding in their hands. Thicker card stock always makes the final product feel higher quality.
Summing it up
Getting your template printed from an online print shop is a great choice. If you still have time, request some samples from the company so you can see and feel different card stocks, finishes, etc. This will give you a better idea of what 60lb, 80lb 100lb, linen, gloss, matte, etc all look and feel like before you get yours printed.