I don't quite understand the issue here.
I went to revisit GTAIV : EFLC and it doesn't use very much of the RX6900XT. Max Settings only gets an average of 40fps. I turned the settings from VERY HIGH to HIGH and it made no difference. I am playing at 3840x2160 resolution.
Yes, I already used "D:\Grand Theft Auto IV - Complete Edition\EFLC\LaunchEFLC.exe" -norestrictions -nomemrestrict
Nothing wrong with your numbers, no issue, GTA IV is an old title from around 2010 perfectly OK with 40 fps.
Graphics Cards around that time did not have 16 GB of Video RAM and monitors were not of such high resolutions.
The recommended Video RAM is a mere 512 MB.
Nothing wrong with using 2.3 GB Video RAM, using more will not give you more fps, the quality of textures is where the extra Video RAM might be used.
Nothing wrong with 57% of GPU, recent GPU running an old game easily, look on the bright side, your GPU will last longer.
Here is a brief guide to more detailed settings, this will give you more fps at almost the best quality, by reducing certain graphic settings.
The favourites would be to reduce Water/Shadow quality, and Anisotropic filter down to x4/x5.
https://steamcommunity.com/sharedfiles/filedetails/?id=1253309779
Experiment and find out.
As you suggested I did in fact go back and turn off Night Shadows and it made a world of difference.
Now an average of 82FPS at a 4k resolution which I'm happy with just not so much not being able to max out completely but it's fine.
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