Small design studio – areas to improve network efficiency?

TL;DR Is my network setup below helping or hurting our LAN efficiency?

I own & run a small design studio (6 employees on high spec iMacs connecting to central file server). We work with lots of enormous files that often have to reference dozens of other files when open (ie Adobe InDesign publications, video projects, presentations, etc) so internal LAN efficiency is critical for us. While we’ve been operating fairly well on our current setup, we’ve been started seeing some pretty inconsistent performance over the past couple of months.

I’m definitely not a trained IT professional, but I’m a huge nerd with this kind of stuff and would consider myself a ‘prosumer’ in the space. But I have a nagging suspicion that my home networking skills have lead to a rookie setup in my studio. Looking for any advice on where I might be going about our setup the wrong way.

Here’s my current setup -

WAN: Spectrum Business 200 / 20Mbps w/ dedicated IP BMC cable modem with dedicated IP > Sonicwall Soho Firewall (DHCP server) > Mac Mini central file server (DNS server) >

LAN: Mac Server > Netgear ProSafe 16 port unmanaged switch > cat5e wiring to 4 hardwired workstations, 4 hardwired printers & plotters, 3 hardwired voip phones (service by Vonage)

WiFi: Apple AirPort Extreme (latest generation) hardwired to Netgear switch. Used by 2 mobile workstations and a dozen or so devices (phones, tablets, appletv, etc) Separate AirPort Extreme hardwired to SonicWall for isolated guest network

File Server: Mac Mini 2016 (top of the line spec at that time-8GB ram, core i7 processor) Mac OS High Sierra, up to date Main Storage: Thunderbolt 3 external raid 5 enclosure, 6TB Redundant backup: identical raid 5 external enclosure Offsite backup: Dropbox enterprise

I’ve been closely monitoring the health & services on our server to see if that’s the culprit of our speed inconsistency. I don’t see anything obvious, so I thought I would shift my focus to the network and see if our setup is appropriate for our size.

One thing I’m curious about is if I would benefit from a managed switch or if our network is too small to see any benefits.