intel core-m processor is underpowered to run autocad
yes it can run autocad but not fast as intel i5
always choose i5 over core-m processor
other than envy 13 that comes with ssd or the ram can be upgraded to 8gb, you can consider these laptops

Lenovo E31-80	Intel i5-6200U, 4GB DDR3 RAM, Intel HD Graphics, 128GB SSD, 13.3" HD, 1.59KG	RM2.4k
Acer Aspire S 13	Intel i5-6200U, 8GB DDR3 RAM, Intel HD, 256 GB SSD, 13.3" IPS FHD, 1.42KG	RM3.4k

m.2 and PCIe are totally different things
M.2, formerly known as the Next Generation Form Factor (NGFF), is a specification for internally mounted computer expansion cards and associated connectors. It replaces the mSATA standard
Buses exposed through the M.2 connector are PCI Express 3.0, Serial ATA (SATA) 3.0

Vostro 5459 i3