If your ultimate concern is about the router being compromised by an external flaw then the choice here is an in-life Cisco firewall - 1,000,000% - even if it's a small business variant.
The amount of drive-by flaw compromise attempts our (commercial) Cisco IPS picks up searching the internet for consumer-brand firewalls is literally insane.
Note that you may need to have active Smartnet cover to download firmware updates. I'm not sure if this applies to the RV series or not as we don't tend to sell those.
What does concern me a little however is that your primary focus is 'security' but you've stated you don't care about web protection, malware protection etc.
90% of attacks begin with a phishing attack. 80% involve DNS at some point of the kill chain. This makes effective web content filtering perhaps the cheapest and easiest way to offer some broader protection.
Relying on endpoint security to deliver this is a bit like playing soccer with a goalkeeper but no defenders.
On that basis - and seeing as you've ruled out PfSense - I'm actually tempted to nudge you toward Draytek. You'll get a respectable SOHO-class router at this price point and their web content filtering is cheap to add.
You could of course go for the Cisco and add OpenDNS
https://www.opendns.com/home-internet-security/