Did you meant you used TCanvas?
As far as I know TCanvas is not hardware accelerated graphics library. It is not optimized for performance and the performance depends on the processor not the graphics card.
For GUI applications and simple games, TCanvas should perform good on modern processor. If you want to get the performance benefit from the graphics card, the you should use graphics libraries or game engines that are hardware accelerated. Like: OpenGL, DirectX, Vulcan, SDL, Allegro, Irrlich, etc.
If your test shows that the canvas drawing performance is almost the same running on i3 and i5 ... well, that's interesting. I wrote some demo games using only TCanvas line drawing feature, it runs much faster on my Core2 Quad computer than Dual Core laptop. Maybe you can show us the code.