replacement HDD for latitude 7480

Any M.2 2280 SSD, NVMe (faster) or SATA (slower) will work as long as it physically fits the system (i.e., don't buy one with a built-in heatsink).

You didn't say which processor you have, and that laptop had several processor options. So, I checked an i5 and an 17 of that generation. Intel says maximum memory speed is 2133 MHz, and it could be less due to motherboard/BIOS support.

You might be able to use faster RAM that would downclock (reduce its speed) to what the system supports. I have used faster RAM in Dell laptops that did downclock to the maximum speed that the system supports. However, some systems can be picky about the RAM they will accommodate, so it's not always possible.

Here are some Crucial RAM sticks that are guaranteed compatible with your system.

You needn't buy a big brand name such as Crucial. I recently bought a relatively unknown brand, Kuesuny, through Amazon for much less than the price of a big brand name, and I'm happy with it. I ran memory tests for a couple of days to thoroughly test the RAM when I first installed it. It performs well and saved me money.

Ideally, you should install a matched pair of identical RAM sticks. Buy those from the vendor as a matched pair. If you are adding to an existing stick, get the same specs and it may work.

Whenever touching components or working inside a computer, wear a grounded wrist strap, also called anti-static wrist strap, ESD wrist strap, or ground bracelet. It's a cheap and sensible precaution. Rest the laptop on an anti-static mat or at least a reasonable alternative such as corrugated cardboard.