Ubuntu settings after adding additional RAM

No, you do not have to make any system changes.
The new RAM size will be detected automatically.

If possible, select a model from the same vendor.
Otherwise, get one with the same specifications.

Some of the important RAM specifications are:

• DIMM (desktop) or SODIMM (notebook) module
• DDR, DDR2, DDR3, or DDR4 RAM
• RAM capacity (in GB)
• RAM speed (in MHz)
  You might mix modules with different speeds or timings,
  but then the slowest settings will be used for all modules.
• voltage
• pin count

Additional information about the usage of swap:
(credits to @Paddy Landau for this contribution)

Swap may be used for high-memory-intensive tasks such as extensive editing of large videos.
Swap is also used for hibernation - if you want to hibernate, swap must have at least the same
size as RAM. If you never intend to hibernate, 4GB swap space will be sufficient for normal use.