The Jentec power brick should be OK. Even it is probably over-kill.
Why use an expensive more bulky boost module? Even if you run the individual VFD digit tubes non-multiplexed at full brightness, brightness, that's less than 0.75A for four so the tiny heatsinks wont be an issue.
Brightness variation across a VFD is far more of a problem with multi-digit ones with horizontal filaments. You should be able to use DC for single digit VFDs without significant issues, however I would advise reversing it occasionally (swap filament connections) to even out the wear on the filament's high emission coating. However, if you are building this as a general purpose VFD driver board and ever want to hook up multi-digit VFDs, the AC filament drive will be essential. You don't actually need to AC couple the filament with the chip you are using, just use a DC coupled full bridge (i.e. a motor driver chip) fed using an adjustable buck converter module to set the filament voltage, and power that off the 12V rail. To compensate for the DC coupling, simply increase the HV rail by half the filament voltage.