Groovyband manages 16 parts (8 automatic accompaniment parts, and 8 parts you can play by yourself). Each of these parts is like a mixer bus to which you can add an insert effect to shape the sound of the playing instruments.
The number of insert effects you can use all at once is limited by two factors: what is available in the hardware (PSR, Tyros, Genos) and what Groovyband allows you to exploit of the hardware capabilities.
Recent PSR keyboards are limited to 4(*) inserts. Tyros models are limited to 7(*) inserts. Genos allows 16 inserts (1 for each channel) all at once. As you can see there is a match between the three Groovyband versions and the three aforementioned hardware models.
This does not mean that you cannot use any version with any hardware. Of course you can, simply do not expect to use what is not availbale either on the hardware or on the software.
Your purchase decision should also be guided by the number of styles available. All the styles available in the Platinum version will sound great even on PSR models. In fact the DEMO version is limited to 4 IFX by conscious choice. If you like what you hear (and we are sure you will!), things can only get better with the more capable software versions.
(*) Including the Variation Effect routed as Insert.