With HD+ and SOD_SP enabled, I attacked a Naga bank and received 8 dragon stones and 4000 gold. I remember that there should be sulfur there (I thought I was playing with my customized SOD_SP options, where the gameplay is as close as possible to the original, but it turns out I missed something). I disabled HD+ and SOD_SP, attacked the bank again, and received the same 8 dragon stones and 4000 gold.
Therefore, either HD+ or SOD_SP affects the contents of the banks even at the stage of launching the game and generating the initial save! So, you need to think about which options to start the game with and choose the option that is necessary for this map and your walkthrough plan at this stage! Enabling/disabling these options during the game will no longer affect the contents of the banks.
In the SOD_SP options (SoD_SP.ini file), I found the following, confirming my assumption:
# Naga Banks provide Sulfur instead of Gems. Requires New Game to take effect.
NagaBank = 0
(Василь Симоненко. Люди – прекрасні)