Lightroom won't benefit Much from the extra RAM unless you are doing panorama stitching and each photo is of sufficiently high resolution.
Photoshop will benefit from more RAM but it depends entirely on your workflow. If you have a lot of layers, then more RAM will help. If you are just adding texts and some simple effects, typically the processor matters more, and in any case, the 16" should leave the 13" far behind. I still have my 2018 13" here and the 16" is by far the faster machine.
I don't use Lightroom much, though. My workflow has shifted towards Capture One. I only launch up Lightroom to look at older catalogs.