That is exactly my suggestion.
I use the 8 port Netgear GS308T with my R4S and have been happy with it. It is also supported by OpenWrt if you prefer to use the same OS on all your devices. However, if I already had a spare Archer C7 and especially if I wanted an AP in the same location as the managed switch, I would use the Archer C7 as a combined dumb AP and managed switch.
What you will be doing if you go this route is very similar to setting up a separate guest or IOT network. This, its linked posts and various posts around them in the threads may help get you started.
Finally, keep in mind that most (nearly all) of the network management will take place on the R4S. You do not want to have more than one device on your network running a DHCP server and handing out IP addresses on the same subnet for example.