16GB is the "sweet spot" for 2024/2025. If you plan to keep this laptop for 3+ years, go for 32GB.
Upgrading the memory is a straightforward DIY task. You can follow detailed visual guides from Dell Support or Parts-People : dell latitude 5430 memory upgrade
Push the locking clips apart to release existing RAM modules. Align the notch on the new module with the tab in the slot. Insert at an angle and press down until you hear a "click". Upgrading Memory on Dell Latitude 5430: A Step-by-Step
Use a Phillips-head screwdriver to loosen the captive screws on the base cover. Gently pry the cover off starting from the hinge side. Safety First: Flip the laptop over so the bottom lid faces up
: 3200 MHz (also supports 2133, 2400, 2666, and 2933 MHz). Slot Count : Two SO-DIMM slots. Maximum Capacity : 64 GB (using 2 x 32 GB modules).
The Dell Latitude 5430 can be "picky" with certain high-performance kits. For the most reliable experience, consider the following manufacturers: Latitude 5430 Setup and Specifications | Dell Singapore