I am currently trying to attempt to transcribe the fourth movement of scheherazade by Nikolai Korsakov-Rimsky and around bars 30+ there is a time signature change which says: 2/8(3/8 6/16). In the beginning of that section, violas have the rythm of 8th 16th 16th 16th 16th with second violins plucking 8th 8th in the same time in a single bar. There are no triplets or duplet markings, to justify which is which. So my question here is do the meters vary from staff to staff, or are the violas in triplets, or violins in duplets and how to make sense of this these time signature anomalies
Based on the sheet music, this looks like a massive case of un-notated triplets to me. (OK, fine, there are some feeble attempts at notating this, such as 6/16 being in the parentheses sets and the quarter note = dotted quarter note sign.) So the violas are in triplets and the violins are in duplets, and each duplet takes the same amount of time as each triplet.
The meter looks like it may vary between each staff(/instrument), but it basically doesn't if you treat this section as having un-notated triplets.