All my bots have passed UK tech inspections with just a removable link and no switch, so unless some events are using modified FRA rules, you don't need a switch. You DO however need a fuse on the main power line that is rated for less than the maximum current that the battery is capable of.

I use an XT90 plug for the removable link and all the similar R/C plugs will do the same job. I like the XT series connectors as they have a shroud around the pins that helps prevent the connector coming apart during impacts and their blocky shape is easy to glue into a home made base.