I think the quantity and variety of LED lighting threads here on OGR is a clue that there is no one-size-fits-all solution. The good news is there are plenty of knowledgeable folks here to answer your questions within the O gauge tent.
So do you already have the LED strip lights you mentioned? What are they?
Above photo from this OGR thread shows the 2 main types of LED strips that you might see for O gauge building lighting. Note how the strips already have the "electronics" (a resistor) to make them directly compatible for operation with 5V DC or 12V DC...both of which are commonly available DC voltages. By commonly available, I mean in the PC world as opposed to our O gauge hamlet where 14V AC is more commonly available!
As a slight sidebar, in preparing my response, I stumbled across this OGR thread showing how even Menards is using LED strips in their buildings!
Actually, in looking at the FedEx building, if you peer under the eaves (or whatever you call it) I wonder if that building too has an LED strip facing downward?
Anyway, what I'm getting at is if you can imagine a "technique" where you standardize on using LED strip lights, then you can eliminate the arguably tedious process of calculating resistor values which seems part-and-parcel of many LED lighting discussions. That is, with 5V LED strips you can get a "cut" resolution of as little as one (1) LED. With 12V LED strips you get a cut resolution of three (3) LEDs...in other words cutting to length means 3, 6, 9, 12, etc.. Again, I'm just musing about a fantasy world where you don't have to mess with "loose" resistors and "loose" LEDs.
If starting from, say, 14V AC from your Z-4000, I suggest an AC-to-DC converter module that just does that...converts 14V AC to either 12V DC or 5V DC:
For example, above photos shows an AC-to-DC converter module (about $5) set to an output of 4.5V DC to power Menards buildings using a train transformer Accessory AC. Note in the lower photo how there is even a mini-voltmeter (about $1) module showing the module set to the proper voltage if you don't have a DC voltmeter handy. Or you could adjust the module to an output voltage of 12V DC if driving 12V LED strips.
Note that Menards chooses to drive the 5V LED strips with only 4.5V as provided by their wall adapters. The reduction if brightness is hardly noticeable and in fact many guys choose to operate Menards buildings at 4.0V or even less to tone down the brightness. Some Menards buildings have hundreds of LEDs which can overwhelm a layout!
I see I'm rambling perhaps about irrelevant matters for your project(s) but if my general direction is in alignment we can continue...
