"Low profile" is a standard size for graphics cards which is half as tall as "full height." Low profile cards usually come with both bracket types so you can install them into both standard desktop systems and SFF (small formfactor) ones.
Be aware that your Lenovo definitely has a whitelist for the Wifi slot and might also not boot unless you source a graphics card from Lenovo with the specific part numbers in the manual. I personally would not spend $125 for a 1GB GT730 or $200 for a 2GB DDR3 model from them, but would consider trying to flash a vBIOS from one of those cards onto a used $5 low-profile GT730 if it doesn't POST.
Whitelist means the motherboard's BIOS is programmed to either not boot if a device not on the list is installed, or the device is just disabled. This is so the company can make more money by forcing you to only buy upgrades from them, which they overprice.
For the PCIe wifi slot, your Lenovo will refuse to boot and only display an "incompatible device" message until you remove the offending card. You may run into the same issue with a PCIe graphics card, so any non-listed card you wish to try should either be really cheap or easily returnable.
@BFG-9000 i did contact lenovo on the phone, they said even though there's a slot, that a graphics card would not work with it the board. Don't think they person on the phone new what was he was doing , though.