Advices on Lightmaps / Baking

Hello,

On my game (target is Oculus Quest) I switched to realtime to mixed lights to optimize performance and overall graphic quality.

I end up with a 42mb lightmap, is it reasonable? I had to remove a lot of objects from the asset scene I used as a starting point but there are still a lot.

Is it the common/optimized/recommended way to compose the scene in unity? Or would it be better to have a large fbx for all the non moving scene objects (floor / walls / trees) and then bake it?

And final question, how do you preview your lighting modifications once you baked it? Sometimes when I move the lights and adjust parameters it seems to work fine and sometimes it's like nothing is going on and I have to bake again. (I had to increment the additional lights per object limit in the lighting settings but it doesn't resolve everything I face while adjusting lights)

Thank you for your help and advices!