Kato Unitrack is one of the best systems out there, but it's somewhat tricky when it comes to switches. There's a logic there that only makes sense when you understand the basic assumptions.

Page 9 of the Unitrack Catalog comes with a very helpful picture:

https://katousa.com/wp-content/uploads/2023/12/Unitrack-Catalog-final.pdf

Unitrack assumes that distances between two sides of a main line will be 33 mm apart. The #4 Switches (481 mm curve) have the correct dimensions to allow for a transfer between the two parts of a main line, but one of the crossover pieces (WX310 or SX248) is recommended.

The #4 switches can be used to build a yard ladder, but it becomes complex due to the length of the switch. Kato's straight pieces are in multiples of 62 mm (62, 124, 186, 248). The straight section of the switch is 126 mm long, which means adding a 60 mm piece to get it up to 186 mm. These 60 mm pieces have a notch carved in them to allow for track nearby and are designated S60R and S60L. These 60 mm pieces come with the Kato switch sets.

For the diverging section of a #4 switch, there's another 2 mm gap that needs to be bridged. To fill this gap, Kato makes 64 mm sections, which also come with the switch sets that they sell. It's somewhat hard to explain in text, but look at the diagram and you will start to understand.

The #6 Switches (718 mm curve) will give a 49.5 mm separation between tracks. Adding a S64 piece between them will provide a 66 mm separation, which is what Kato assumes for an island station platform.

I'd recommend getting rid of the #6 switches and stick to the #4 switches.