Almost all enemies and bosses have had they're hitboxed enlarged. After reading a lot of reviews, I understood small hitboxes to be a big issue. So they have been adjusted, I'd guess 33% larger, som less, some more. Fast moving insects will still be difficult to hit, but more forgiving.
The vignette can be switched off in the main menu.
The HUD can be toggled visible/hidden by a key. This is for taking screenshots without the HUD with the steam overlay.
(Warning: Onscreen messages, healthstatus and so on will not be visible while it is hidden)
When taking a screenshot with the internal game system, the HUD + vignette is automatically momentarily removed for the image.