You are asking question that are probably better answered by a consultant or specialist.
iX systems would be one source on what the TrueNAS systems can handle and the issue of separate TrueNAS systems for disk and flash storage.
You also look like you should consider fiber networking from your description of your current setup and not knowing where you are on the small to medium enterprise scale, SME. You talk of mixing database, small and large files and we don’t know if you use different datasets for different data types. Block storage? Current pool size, data growth rate and how full your current sets are now? Expected expansion of the current and future system.
Have you looked at backup solutions like Veeam for your Windows VM (Revit)
Adding link on 10G base T
https://forums.truenas.com/t/10gbase-t-best-to-avoid-it-if-you-can/1594