Hello & Welcome to the Forum!
Here is MY answer to your power needs question.
Assemble yout track and the passing loop, connect your power pack & turn it on, all the way up.
IF you own a multi meter, now is the time to break that puppy out.
If you don't own one, borrow or buy an inexpensive one.
Set the meter for the correct ac/dc - voltage.
Using the meter, check the voltage supplied at the track terminal.
Using that voltage as your base, check around the track & passung loop to see if/how much line loss you have.
If significant at furthest point from track terminal, you'll need either additional power feeds for more power around the layout.
If you have dead spots, check the track connections.
Use either terminal tracks or solder feeder lines to your track.
Hope this helps.
Happy Rails!
dave