I've been biamping VSA speakers for years, across three different models. Currently, I'm using Tortuga LDR attenuators for both the primary preamp/controller that switches between inputs and another one with only one input to adjust the level of the bass amps. I would recommend using a primary controller and bass amp attenuator that can be adjusted from the listening position. Once you have the capability to fine tune the level of the bass amp relative to the mid/treble amp, you really come to appreciate the control.
I've found that different recording labels have very different approaches to the bass/mid-treble balance. For example, the bass on Naxos recordings is unfortunately not as extended or dynamic as it should be. In a word, it sounds polite. I frequently bump the bass one or two dB's compared to, say, a London/Decca. Similarly, different streaming services each have their own frequency profiles and often need a bass amp adjustment up or down a dB or so.
One other recommendation that I'd make is that the primary preamp/controller should include the capability to toggle the absolute phase of the system... from the remote. Once you use that for a while, you won't want to be without it. FYI, my Tortuga LDRxB has that feature. The difference between the right and wrong setting is clearly audible on a reasonably good system. Unfortunately, there's no consistency between labels (and even recordings within one label), so you'll need to confirm that you have the right setting for each recording.