Of course it depends on what you want to achieve…
Do you have high technical quality of the print, there must be enough pixels. Since it also depends on image content. Black background with a white dot manage with a few pixels. Much detail and great dynamics places much higher demands.
Do not any of the image in the size you want. Tell me instead what size the image area should have and any white border. I use a special print program interpolates the image to the right size and it does a better job than PhotoShop. In addition, sharpens the picture better, without the risk of over tightening or artifacts. There are not enough pixels to print needs to add pixels, so-called interpolation. This is to get enough pixels to get a good print. It is easy to over tighten a picture and it might look good on screen, but on a printing visible artifacts clearly. Avoid therefore also sharpening for printing when you send images to me.
If you want to simulate the print on the screen, you can make it through the so-called “soft proofing”. Please download the paper profile of the paper you want and make a simulation in PhotoShop. This is particularly important when printing on matte paper. The prerequisite is of course that you have a calibrated monitor and correct the lighting in the room.
Avoid self-destructive as .jpg, it is for the Web. Send any files in .psd (Photoshop's own format) or .tiff. Also use the Adobe RGB through the entire flow, the smaller sRGB color space is for the Web.