RMerlin

It would have benefited all involved. Are you seeking truth or a side? This isn't about Linus and reaching a company for comment before publication is common practice when reporting a bombshell-style report. This had zero advantage to benefit Linus or LMG except to add genuine context of which is important.

Everyone loves drama, but drama hurts real people and affects lives.

I dropped RT-AC87 support a few years ago, so that's not an option if you want DNS over TLS support.  That router has also been EOL by Asus for quite some time now.
 
https://www.asus.com/event/network/EOL-product/
 
With Asuswrt-Merlin, the DNS over TLS queries are done by the router, and in a typical setup, your LAN clients will use the router as their DNS server (which will in turn use DoT).
 
Some clients have hardcoded DNS servers (like the Netflix Android app for instance).  The workaround with Asuswrt-Merlin is to enable DNSFilter, and force all clients to use the Router as their DNS server when they use regular DNS queries.  You can also have the router disable the automatic DoH promotion that is supported by newer Windows and Firefox clients, however anything that arbitrarily decides to use DoH will not be intercepted by the router.
 
All of this however will require a newer supported router.
 

If you already have Wifi 6 devices (that is devices with 802.11ax support), then it's definitely worth it, especially as Wifi 6 improvements start bringing actual benefits when you have two or more of them connected at the same time (more efficient bandwidth allocation).  It might then be a matter of budget.  Mid-range AX routers have started to appear on the market now, like the Asus RT-AX58U/RT-AX3000, so these would be good candidates.  I'm having a hard time recommending to overpay for a high-end Wifi 6 router however (like the Asus RT-AX88U), as the improvements over Wifi 5 rarely justify the current price premium these routers carry.

@RMerlin Just to follow up, we did end up getting the RT-AX3000 you'd recommended, and it went in good. I was initially a bit worried by reports that it had shorter range, but it has at least asuch range as the unit that was in there before, and now we're getting ~450mbps+ on all of the devices very hooked onto it so far. 
 
Thank you very much. Its looking like it's going to be a very nice upgrade. 

It depends how his system is set up.  It might make more sense to just disable the Wifi on the main router and use the mesh system to cover the area near to that router for example, to ensure centralized client management.  You generally wouldn't want to mix up mesh and non-mesh APs, as it might prevent roaming from working properly.
 
We`ll need more info as to how everything is setup first.

If you already have Wifi 6 devices (that is devices with 802.11ax support), then it's definitely worth it, especially as Wifi 6 improvements start bringing actual benefits when you have two or more of them connected at the same time (more efficient bandwidth allocation).  It might then be a matter of budget.  Mid-range AX routers have started to appear on the market now, like the Asus RT-AX58U/RT-AX3000, so these would be good candidates.  I'm having a hard time recommending to overpay for a high-end Wifi 6 router however (like the Asus RT-AX88U), as the improvements over Wifi 5 rarely justify the current price premium these routers carry.

I have an Asus RT-AX3000 and I love it. I feel like Asus's firmware is the best of any stock router firmware I've used.
It also supports Asus-Merlin firmware if you're into that.
 
The RT-AX3000 is around $179 USD or $239 Maple Syrups if you're in Canada.
 
Edit: I just noticed the Merlin firmware dev posted in this thread, Hi

And note that 6 GHz wifi is actually branded "Wifi 6E".  Not every future Wifi 6 router will be Wifi 6E, as this generally involves adding a third radio dedicated to the 6 GHz band (that is at least the path that most manufacturers are going with at this point).  Because of this, I expect Wifi 6e to be a niche platform, and the majority of mid-range wifi routers will still be only 2.4 and 5 GHz.
 
BTW, by your use of the labels "Wifi 2 and Wifi 5", I believe you are mixing up bands and classes.
 
Wifi 5 = 802.11ac, which supports both 2.4 GHz and 5 GHz band
Wifi 6 = 802.11ax, which also supports both 2.4 and 5 GHz bands, but also has a few extra optional features such as OFDMA, supports more streams, etc...
Wifi 6e = 802.11ax, which again supports both 2.4 and 5 GHz bands, but also adds support for the 6 GHz band
 
Yes, you should definitely use the 5 GHz band whenever possible, as it will be much faster and less congested than the 2.4 GHz band.  Ideally, 2.4 GHz should only be used for devices that require less bandwidth, like an IoT device.

Modem/router combos tend to provide very poor router implementations.  They rarely get proper security updates, and they provide very basic functionality.  I've seen some of these also have anemic CPUs, where just navigating the webui can take 30-60 seconds per page to load (I'm looking at you, Bell Canada's HomeHub 2000...).
 
Another reason not to get a modem/router combo: if you ever wanted to, say, upgrade the modem from DOCSIS 3.0 to 3.1 due to a service upgrade, or upgrade the router from Wifi 5 to Wifi 6.  Having both of them bundled together will seriously limit your ability to upgrade.
 

Modem/router combos tend to provide very poor router implementations.  They rarely get proper security updates, and they provide very basic functionality.  I've seen some of these also have anemic CPUs, where just navigating the webui can take 30-60 seconds per page to load (I'm looking at you, Bell Canada's HomeHub 2000...).
 
Another reason not to get a modem/router combo: if you ever wanted to, say, upgrade the modem from DOCSIS 3.0 to 3.1 due to a service upgrade, or upgrade the router from Wifi 5 to Wifi 6.  Having both of them bundled together will seriously limit your ability to upgrade.