PM from OP.
sorry if i was unclear i meant an adapter like this one M2 PCIe SSD Adapter X110 Would this work without causing a bottleneck large enough to make it run at roughly the same speed as a SATA SSD
The pci express x1 slot is free on the motherboard
Adapters require boot support and, on an OEM system - there's no guarantee it would just "work".
Most PCIe M.2 SSDs are x4. Running on older chipsets limit to x2, which impacts speed substantially..... Only connecting it to an x1 slot would limit it further.
The x1 slot is PCIe 2.0, limiting max theoretical transfer speeds to 500MB/s vs SATA3 at 750MB/s.
While "real world" usage isn't likely to 'feel' much slower, using a PCIe SSD in an x1 slot would actually limit speeds below that available via SATA3..... at least theoretically.
Between boot support (or lack thereof), the limited speeds of x1, and the added cost of an M.2 drive + adapter, I don't see any justifiable reason not to just pick up a 2.5" SATA SSD.