Working on an 8 inch x 8 inch canvas for space
I made the envelope approximately 16cm x 11cm at 300 pixels per inch
applied texture old paper at default setting but changed the size to 300 and depth to 6
Add a slight bevel to the card and envelope
You could use your lighten and darken tool to give a bit more dimension to the edges of the envelope and card
Merge when satisfied and crop to size.
Image shown at 72 pixels per inch and 600 pixels x 600 pixels Smart Size