Hey Iulian, In VoiceRack FX, the number of effects you can use at once is limited to what each preset has. "Preset" is very literal with this app. Some presets have two effects active, like ones with doubling and reverb together, but you won't be able to use like 10 effects at the same time. Most presets are just one effect. I think the aim of this app was to be as simple and low cost as possible, so there isn't a whole lot of preset customization. This video gives a pretty decent idea of what VoiceRack FX is capable of (although I wish Mitch sang a little more, haha).
Perhaps you're thinking of VoiceJam Studio though... that's the app with looping capabilities. With that app, you can only have one tempo at a time by which all loop slots abide. Effects follow the same rules as VoiceRack FX, so you're also limited to premade presets. Here is a good demo of VoiceJam Studio in action.