No matter how much I try, I can never remember every little detail about RED. I just remember that the more PS2 tiling you have is a bad thing and you can reduce it by scaling the texture maps down in RED.
Using this technique I built a map 64H 768W 1152D and applied textures with 0 PS2 faces.
I remember when I first got into RF mapping in 2001 I was lucky enough to have met black seer to guide me through the beginning of it. I wrote to him one day and asked him why my map was crashing, he asked me how much ps2 tiling is their and I replayed with +2000. Yep he just loled at me.
I would say Apply Map to everything, but make sure the faces of brushes aren't anymore than 20x20 RED units. eg. Your 100x100x100 brush should have at least 5 splits along each axis. You can create splits in brushes before you begin building them, alternatively you can try clipping a brush [doesn't always work] if it has already been built.
You won't need to worry about scaling textures or brushes and you will also be able to Apply Map so that the textures will always look nice [not stretched].
This also works
A common mistake people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.
I forgot what number it was. It was something like if you had under 11 PS2 faces, the map would usually crash when you did geo-modding. It's been a while, so I have forgotten a lot about RED.