Above is a cut-out from one of my  photos.
A preview of the the whole picture (heavily compressed) is below:

In other words, the pictures have an excellent resolution and are certainly good enough to print on a hi-gloss, high-resolution printer in US-LETTER or A4 size.
The actual pixel-resolution varies from around 2000 to 4000 pixels width.
The picture will be emailed to you in JPG format. JPG-compression is set to "less compression -- best quality", the resulting file-size (depending on motif) can range from around 0.5 to 4 megabytes.