John-
My train room is a former 18x30' fiberglass and steel frame greenhouse.
The ceiling needed to be replaced since the filon panels leaked. It's now a series of aluminum/styrofoam sandwich panels.
The crushed rock floor was replaced with a concrete slab and the evaporative cooler was replaced with a window air conditioner supplemented by a portable.
I still use the overhead gas heater I used when it was a greenhouse.
I opted to cover most of the walls with 4x8 plastic sandwich panels with insulation wedged between the panels and the fiberglass. This was done primarily for two reasons. The first was that of trying to get some control over temperature. The second was to provide a surface for backdrops.
Most folks will warn you against fluorescent lighting. I use it. However, I only have the stock currently in use actually on the layout. The balance is stored in a series of utility carts which slide under the layout.
I can't really discuss scale related issues since it's my understanding that your primary layout is HO. Mine is 3 rail O with an emphasis on 1/4 scale.
I only run TMCC command and don't run conventional. So, the power comes from a series of Lionel Track Power Controllers (TPC's) and 180w Lionel power packs.
Although I have a control panel, I don't use it very much. Such things as switching are now also controlled using Lionel SC-2 switch controllers. About the only thing I still use the control panel for is uncoupling. I haven't rigged them for TMCC control. Might someday.
I use AtlasO track and switches.
My response is probably a bit of overkill to your basic lighting question.
Structure and vehicle lighting are 12VDC warm whites. I have a separate power supply for this function. I use LED's from Evan Designs (
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). I also like their Model Builder software package for such things as making scale signs. Their import function is quite handy for making unique signs and you can select the desired scale.
Hope this helps.