New to Opnsense. Looking for a Cisco RV340 backup

[Jarvar]

Hello Everybody,
I am quite new to Opnsese. I first fired up pfsense and then discovered there was opnsense so I've been using that for the past couple weeks through a VM on Proxmox.

There are a couple offices I have been doing work for. When they first started, it was 1 computer and so they just stuck with a SOHO router from Asus, the RT-AC68U which was quite good. It had OPENVPN, WOL, 802.11AC and the ability to setup Guest WIFI and both 2.4 and 5GHZ.

Admitedly, I am still using this for my own home setup.
However, they have since grown to 6 workstation computers, 1 windows 2019 server, 1 Network Printer and 4 Yealink VOIP phones. At one location, I was fairly knew and some people gave me the advice of using something like a Sonicall TZ or Fortinet. We went with a Sonicwall TZ500 a couple years ago for what seemed like an exhorbiant sum of money for a UTM based firewall. Unfortunately, a year after, the subscription was ending and I was introduced to different models of Firewalls and Routers and was able to get the CISCO RV340 working at another location.

We haven't moved in that direction yet, but eventually we could create a VPN tunnel to link the two sites, or investigate some type of SD-WAN or cloud alternative. It seems like the landscape is changing fast.
In the end I switched over to a CISCO RV340 as well, but did not sign up for any of their Cisco Umbrella Services.

Are there any recommendations on what I should get to replace or upgrade something similar? Are there higher recommendations?
I saw recently on FB somebody recommending the Dell Optiplex 7010 or 3010 with a low profile NIC card. Is there anything rack mountable? Or will those fit on a 1u-2u rack shelf? They usually have a premium on shellf space in these smaller dental offices which is where it will go.
The other suggestions are Netgate, Qotcom?
I am looking at a device which I can setup as backup and implement in case one of their routers/firewalls go down.
The recommendation from CISCO was to get a backup device since we have 2 locations running this device already.
Surprisingly the RV340 has a lifetime warranty and support even without the subscriptions for around $250 CAD. I am tempted to go with them for a backup device, but hoping I can nudge the offices towards opnsense in the future...
I would welcome any feedback or recommendations. I am quite new to this.
Thank you very much.