sorry to double post. ziggy, do you have a link to all those hacks/improvements? I found an english patched rom however I'd like to check out the other options.
The YZB hack seems to be final. The other two hacks, neither has been updated recently but hopefully they aren't abandoned. I haven't been keeping up with either, to be honest, so I don't know if any news exists regarding future updates.
I'm parting with some duplicate Blu-Ray and DVD movies. Check out this thread if interested.
The major thing it does is remove the black bars at the top and bottom of the screen. Now the game is in full screen! There's also some bug fixes and a couple QoL improvements.
I haven't had much time to dive into them but I've been playing the worst versions of Castlevania: the MS-DOS port and the Commodore 64 port. These are probably not what fans look fondly back on. I didn't know they even existed until a few years ago.