Top note mono voices came out in the 70s and were fitted to virtually all organs; arrangers achieve this using the right hand auto chord feature. (One of the many menu options)

Bass to lower has been available on organs from the 70s with arrangers adding the feature in the 90s. (You will find it in the chord recognition menu)

VA (Virtual Acoustic) voices were introduced by Yamaha in the 90s with the EL 00 series and use sound modelling rather than just sampling, (A lot of organ manufactures use their own variations) and are more flexible than the layer switching (SA/SA2 voices) of Yamaha Arrangers.

Switches on the side of expression pedals (Arrangers are just volume pedals) came about because all the organist limbs were doing other things, however as most arranger players don’t have bass pedals, standard foot switches can be used.

Organ mode (Different manufactures have their own names) has also been around for decades.

Remember organs are designed to be played, with the extra features added to allow more expressive playing, whereas arrangers are easy play (Press a button and everything is done for you) designed for the home hobby player who wants to sound good with minimal effort. (The exception is Lowrey Organs who take easy play to a whole new level, but can still be played as an organ)

Bill