Yes, it is possible to use an event value for Segment events. When sending events from Segment to Statsig, anything in the properties field of the Segment event is treated as the event metadata field on Statsig's end. This can include an event value. For instance, you can use this field to specify the type of achievement that was unlocked, or the name of the product that was added to cart, or the price of the item that was purchased. However, the specific implementation details might need to be confirmed with the Statsig team.
When it comes to the Autotune configuration, it's important to note that it currently doesn’t support optimizing for the value on an event. Autotune can only be configured to optimize for the count or occurrence of an event. For example, if you want to pick the variation that will have the most number of success events, you pick that event.