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What locomotives will you run? That tells you how many amps you need.
Looks like you want to use LGB track?
Will you fasten the track to something?

 

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Since you want to install on a deck....I have used the lgb track connectors that fit into the notch in the tie and keeps the track pieces together. Its LGB 11500. I have pets and kids. The tracks can be stepped on and take it well. But they disconnect. Part of LGB ads was that they had a Mercedes parked on the track

The 11500 connector is a cheap alternative to railclamps until you see the need for those.

 

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Lgb part 10260 insulates. It replaces joiner 10001. See the tab on the metal joiner, so it resists coming off the rail.
There are also insulator track pieces pre fab that have been made over the years, some looked like a grade crossing, some were accessories to signals and are just a short track with a gapped piece of rail. There are mainy examples of those, 1015u, 10152, 10153 etc
Mind you the 4 digit catalog numbers are now getting 40 years old, so unless you like the style buy a 5 digit catalog number.
Personally I would go with a track piece instead of the plastic joiners

 

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In that case please isolate both tracks, dont use the single track isolation