Don't use those insulated connectors. Use the non insulated and shrink tube them.
Always use a toothed crimper on non insulated. This Klein 1005 is a great tool.
https://www.kleintools.com/catalog/combination-cutting-tools/crimping-and-cutting-tool-connectors
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No solder required. Solder is not a good conductor. There are times I use solder to help "lock" a connection, it is not used to improve the connection.
