The most important question here is if you are intending to use this Menard’s product with the post war New York Central F3 set you have been talking about and showing in other posts.
As you mentioned on one thread, you were going to get a tested/refurbished KW from somewhere. (glad to see you got the one you had checked out). You would NOT want to use this Menard’s product at the same time on the same loop of track as a KW!
Anyway, the post war F3 needs something to vary the voltage at the track, such as the KW (or any other post war or even modern transformer that will vary the AC voltage applied to the track).
The Menard’s item you pictured does exactly what the description says, it applies a constant 18 Volts to the track. It is also 18 Volts DC, not AC like a KW! This Menard’s item is also NOT a controllable variable voltage like the output of a post war transformer when you move the handle.
It is also NOT advisable (even if not for the issue of having AC for one source and DC for the other) to put 2 voltage sources to the same loop of track if it is not broken down into insulated blocks (meaning if you do insulate the center rail of the track into “blocks”, it prevents the transformers outputs from being applied to the same continuous piece of metal of the center rail of a single loop). Without insulated center rail sections, this results in what is called putting the sources (transformers) in parallel, which is a major no-no for 99% of how O Gauge AC powered trains are run.
The bottom line is in simple terms, that Menard’s product is meant for the type of trains they sell, which are designed to be run on a constant DC voltage supplied by the power “brick”, and then the remote that comes with the engines takes care of controlling that voltage with electronic circuitry to change the speed of the train.
You need something that varies the voltage to the track itself with that post war F3 set, so this is not a good match.
For addressing power drop outs, you can use multiple lock-ons. The traditional Lionel style ones (I think you had one shown hanging on the wires in your original pictures of your stuff), but also were made by MTH and probably other companies if you can find them. You would install them at various places around the loop of track. Using wire and your choice of splicing methods (barrier strips, wire nuts, etc.) you would tie all of the center rail feeder wires together to go to one post of the transformer (A or B on a KW) and tie all of the outer rail feeder wires together to go to the common post (U on the KW). I’d probably recommend using 18 gauge or larger, so 16 would be OK, something like 12 is probably way overkill for your intended use, most likely, and 22 gauge is way too small. (wire sizes get bigger as the wire gauge number gets smaller)