Huh so a Pi 5 is basically a Core 2 Quad according to Geekbench 6, that's fun. It was part of the recommended specs for GTA 4 back in the day, it should run great.
One advantage of DXVK in this regard is that it fixes a lot of the native stutter present on the PC version of GTA IV: https://youtu.be/aUIhtXzdeZY?t=218