what's the right scale

i’m just starting to get back into model railroading what is the right size scale car’s & trucks to use for my HO lay out 1:87 or 1:64 i just bought a bunch of 1:87 trucks

You made the right choice. HO is 1:87. The larger 1:64 cars and trucks are S scale.

1:87.1 scale is what you are looking for. But what you said

just reminded about forced perspective. You can buy things from smaller scales and put them as far away from the edge as possible.

This rarely works in real life unless you can control the angles from which people view the scene, however.