I am making a 3D tank game prototype with some physics simulation, am using C++. One of the decisions I need to make is the scale of the game world in relation to reality. For example, I could consider 1 in-game unit of measurement to correspond to 1 meter in reality. This feels intuitive, but I feel like I might be missing something.

I can think of the following as potential problems:

1. 3D modelling program compatibility. (?)
2. Numerical accuracy. (Does this matter?) Especially at large scales, how games like Battlefield have huge maps: How don't they lose numerical accuracy if they use 1:1 mapping with real world scale, since floating point representation tend to lose more precision with larger numbers (e.g. with ray casting, physics simulation)?
3. Gameplay. I don't want the movement of units to feel slow or fast while using almost real world values like -9.8 m/s^2 for gravity. (This might be subjective.)
4. Is it ok to scale up/down imported assets or it's best fit with a world with its original scale?
5. Rendering performance. Are large meshes with the same vertex count slower to render?

I'm wondering if I should split this into multiple questions...