You can adjust default settings at the top of the Tween.ash file:

// Max number of simultaneous tweens that this module can play
// Feel free to change this number, but the higher it is, the slower it might be
// So just increase or decrease it to however many you need.
#define Tween_MAX_INSTANCES 64

// If true, it stops all tweens upon leaving the room
// If false, it stops most tweens except Audio, GUI, and some screen-related tweens.
#define Tween_STOP_ALL_ON_LEAVE_ROOM false

// Default TweenEasingType
#define Tween_EASING_TYPE eEaseLinearTween // All Tweens Except GUI and GUI element Tweens
#define Tween_EASING_TYPE_GUI eEaseLinearTween // For GUI and GUI element Tweens Only
#define Tween_EASING_TYPE_AUDIO eEaseLinearTween // For Audio Tweens Only

// Default TweenStyle
#define Tween_STYLE eBlockTween // All Tweens Except GUI and GUI element Tweens
#define Tween_STYLE_GUI eBlockTween // For GUI and GUI element Tweens Only
#define Tween_STYLE_AUDIO eNoBlockTween // For Audio Tweens only
#ifver 3.4.0
#define Tween_STYLE_PROPERTY eNoBlockTween // For Property Tweening only

// Default TweenStopResult
#define Tween_STOP_RESULT ePauseTween // The expected behavior for stopping all tweens

// Default startDelay
#define Tween_START_DELAY 0
#define Tween_START_DELAY_GUI 0
#define Tween_START_DELAY_AUDIO 0

// Default TweenTimingType
#define Tween_TIMING eTweenSeconds
#define Tween_TIMING_GUI eTweenSeconds
#define Tween_TIMING_AUDIO eTweenSeconds

These allow you to change the defaults in some of the tween.

For example, by default all GUI tweens are blocking (eBlockTween). If you would like to start with all non-blocking tweens instead, you can change the definition of Tween_EASING_TYPE_GUI to:

#define Tween_STYLE_GUI eNoBlockTween