The best thing about KB is the keybinds!

As someone who doesn't use WASD to move around in xiv and only uses the mouse, I have the first 6 actions on my second hotbars set to QWERTY. For me its faster and easier than ctrl or alt and it fits all the actions I commonly use in combat.
So for instance on whm, healing is on 1,2,3,etc and dps are Q,W,E,etc. Makes bouncing between them super easy. RDM my basic magic and physical rotations are 1,2,3,etc and my aoes are Q,W,E,etc

F-keys I have set to mounts and sprint. F1 sprint, F2 Legacy Chocobo F3 Kirin and so on...

I also keybound everything I use even semi regularly and changed others to more comfortable positions. Even have a key to mute my game, which I used more often than I ever thought I would. Every key on my numpad is even bound to something, from switching jobs to deciding which UI elements are displayed at any given time. I love that with 1 click 80% of my UI disappears.

Just go all out, there is no limit to KB usage. I honestly have no idea how anyone plays some of these games on a controller, its so restrictive. RDR2....massively better with a KB for instance. FFXIV I could not imagine the nightmare a controller would be with as many buttons as I use.