gtktitlebar VS adw-gtk3

I use GTK Title Bar

Wouldn't you by any chance be using the Extension GTK title bar? It removes the title bar of non gtk apps in full screen.

I would also like to propose an alternate solution: keep the thicc titlebars, and instead, use this extension to automatically hide the titlebars when your windows are maximized/tiled. I don't so much mind big titlebars when my windows are floating - I'd like them to have SOME grippable handles so I'm not always moving all of my windows with Super+Left Click, but when they're maximized, I just don't need the grip yaknow. Especially because clicking+dragging on the top panel when a window is maximized will move the window, I just don't need the titlebar then.

I'm not 100% sure what you mean, but for non-GTK applications, https://extensions.gnome.org/extension/1732/gtk-title-bar/ <--- that extension really helps make things look nicer.

yes, you can remove it with this extension https://extensions.gnome.org/extension/1732/gtk-title-bar/

GTK Title Bar extension makes the experience much better.

You can't. That's the main disadvantage of Gnome IMO (other than usability). GTK apps just look like trash, there's nothing you can do about it, and Gnome comes with a lot of them. I guess this extension can make it better. It's not ideal but it's the best solution I've found.

For GTK apps, the title bar size is determined by it's buttons. For non GTK apps you might try this extension

Use this theme

As far as I know it doesn't exist yet... but most likely Evince will be ported in the future. But while that doesn't happen, what you can do is use the adw-gtk3 theme (https://github.com/lassekongo83/adw-gtk3) for legacy applications to combine with applications that are already ported to libadwaita

Why not use the adw-gtk theme for gnome to make all the deco's match rather than use Adwaita-Dark?

Application Theme : adw-gtk-3 with Gradience

You can use the adw gtk3 theme. https://github.com/lassekongo83/adw-gtk3

GTK theme: adw-gtk3

That's because i use this KvLibadwaita and adw-gtk3 themes to have everything looking the same on Gnome :>

Just found a workaround for the issue until an update fixes the issue for Fedora 28 - Alt+F2, type "r" to restart Gnome Shell. More info: https://github.com/lassekongo83/adw-gtk3/issues/213

I believe that adw-gtk3 could still be beneficial in ensuring a uniform appearance across both GTK3 and GTK4 applications. The more solutions we can offer to users, the greater the likelihood of achieving the desired outcome.