Hi,
Max RAM will be 32GB of DDR4 2400MHz RAM (2x16GB) even if service manual talks about 16GB
On page 25 of service manual you can see the steps to install the RAM
http://h10032.www1.hp.com/ctg/Manual/c05527167
While you are in the notebook, check if it has the M2 slot on the motherboard

If the slot is there you can install an M2 PCIe NVMe SSD of your preferred brand and capacity. Something like the Samsung 970 Evo Plus would be great. The install the OS on the SSD and keep the hard drive for storage (or just remove it). It would give an amazing boost to the everyday performance of the machine. Much more than the extra RAM.
Hope it helps,
David
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