Try finding useful specifications for a notebook. The internals vary so much from country to country. Different factories. Different products in the same plastic case.
Some of the X540 series have a DVD player you can replace with a disk which means you can move the 1TB to the DVD slot and put an SSD in the disk slot.
Some have 4 GB RAM soldered in and a slot for up to 8 GB more. As I mentioned earlier, 4 GB is fine if not editing big scans or video or playing a big game. DOOM 2 is the ultimate game and runs in 2 GB. Why would you play anything else?
Complaints about 4 GB are usually from users of Chrome after they open 768 Web pages.
You can run a good speed test from a USB stick if the USB stick is fast, something like a Sandisk Extreme. They are as fast or faster than old magnetic disks. An Extreme Pro is closer to what you would get from an SSD upgrade.