1. Is the HUD fully customizable like on PC?
2. Can you have keyboard hotbars?
3. Is the frame rate capped at 30 or 60 FPS?
4. Does the FPS drop much in light party events and do actions ever lag?
5. Does a SSD help a lot?
3. Yes, I believe. Can't say for sure, though.
4. Depends on what your light party is doing. And where. Actions definitely lag in very crowded areas. You can turn off effects animations of other players to alleviate some of this.
5. Can't really say. Don't have one.
1.) No. The missing components are regular on-screen Hotbars, the Mini-icon bar, Inventory grid, Gil display, the ability to dock additional chat boxes, and direct keyboard Keybinds for the Mount and Sprint abilities (or basically anything you need to have on a regular Hotbar to directly keybind).
5. You mean if you have the PC version? I'm going to go with yes. I upgraded to a SSD in between beta and release and (besides the nearly instant Windows load on start-up) it seems that in FFXIV areas load faster when crossing a zoneline. Could just be my imagination.