how many Lionel 36w 1.8 amp accessory transformers for accessories?

I would use a 100 watt starter set type transformers. Use a 12 or 14 V accessory tap. Bulbs can be as much as 4 watts a piece,depending on the bulb and voltage. The 36 W might work if you cut the voltage down and light the shantys with LEDs.

Not sure what the "switches"  are. If you mean turnouts it is best to use a separate tap.

If you have the room bigger is always better,the wider the curves the better,whatever space you allow. You can do a lot more on a 5X9 layout than a 4X8. Search the forum,there are many posts on bench work and methods. As far as wiring,I drill holes,and put the wire through,then wire underneath. I am wiring now. I am doing a large layout,there are a few pics on my wiring methods here

LINK

Glad to see you back in the hobby and welcome to the Forum.

Dale H

I agree with Dale. If you have the space, use a couple more sheets of plywood and make it 5' wide. Cut a sheet on it's length to 5' long x 4' wide. Then put the 4' sides together. Try to keep the switches in the center or near the front.

That would let build an 048 outer and 036 inner loop with switches for crossovers and siding and perhaps a reversing loop.

yep, keep your wiring underneath. Put holes in the framing and pull the track and accessory bus(s) before putting the deck on. Same as the channel on the top, less work and wood waste.

You have the small handles of the ZW that can drive your accessories. B & C channels.