Read the details about DNS security .. easy to find.
eg. https://blog.cloudflare.com/dns-encryption-explained/
Using unencrypted DNS allows someone (in the middle, ie ISP, coffee shop, home network) to track your web browsing.
Is it the issue of the insecurity of sending requests to go to a particular website address in text - being thus insecure?
Yes.
It is possible to also inject fake addresses to get you browsing fake websites for nefarious purposes.
Or giving you even more ads.. from everyone along the route.
Do I address this through my browser's security settings?
In some cases yes. Or at the OS level.
https://www.cnet.com/tech/computing/safari-gets-new-encryption-option-for-network-privacy-on-iphones-macs/
I would note if you are doing normal web browsing etc.. you are being tracked anyway. Cookies and all the social media and search engines etc are definitely compiling a comprehensive list of your shopping needs.
For most people this is kinda irrelevant but if you visit the dark web.. well tracking is what authorities are doing.. as well as the nasties.
192.168.1.1 is just your DNS cache in the router.. It helps to speed up your regular searches. This is mostly irrelevant today with very high speed low latency broadband.. but if you are stuck on low speed/high latency connections does help.
You can easily switch to more secure DNS server
https://au.pcmag.com/security/62160/how-and-why-to-change-your-dns-server