Advice for upgrading home system by adding a OpenWrt Router

I need advice on upgrading a home system.

My 2-story house is roughly 2400 sq. ft., w/ an adjacent 240 sq. ft. cottage approximately 30 ft away from the house. The furthest point of the cottage is 50 ft. from the house.

Currently I'm running a Linksys WRT 1900 ACS v. 1 router with stock firmware and the Linksys WRT004ANT high-gain antennas. The router is located in our wiring closet on the second floor of the house. We also have a Linksys range extender in the cottage, but wireless connectivity there is still poor. So I want to upgrade the system and am considering a few alternatives.

Please note that below I mention Linksys hardware because I already own a Linksys router and I'm familiar with Linksys products. But I'm not wedded to Linksys. If there are better choices, please suggest them.

At a minimum, the upgraded system should have these features:

  • Guest network (we often rent out the cottage)
  • Sufficient strength to serve the cottage satisfactorily
  • Run OpenVPN
  • Can use several free dynamic DNS services (e.g., no-ip, dynn.com, zonomi)
  • Can use Cloudfare
  • Support 4+ 1GB wired ports

I realize some of these features are available on many routers, but in my experience some routers make it less painful than others.

Right now I'm primarily considering one of three options, but I'm open to your advice.

Option 1: Upgrade to 2-router OpenWrt system
Replace the 1900ACS with a more powerful router, such as a Linksys WRT3200ACM (or equivalent), and convert the 1900ACS into bridge mode. This option would include:

  • Install OpenWrt firmware on both routers, and use the new firmware to increase their transmit power
  • Replace the 1900 with the 3200 in the wiring closet
  • Relocate the 1900 to the downstairs bedroom closest to the cottage. It would be connected to the network by Ethernet cable, run in bridge mode, and be located about 10 ft. from the house's wall nearest the cottage (i.e., ~ 40 ft. from the nearest cottage wall and ~ 60 ft. from the cottage's furthest wall).
  • Possibly add a set of high-gain antennas to the new router.

Option 2
The same as Option 1, except using a WiFi 6 router instead of the 3200. During Cyber Week I was able to order a Linksys MR9600 for $200. I realize the MR9600 is not the greatest WiFi 6 router, and it's currently not supported by OpenWrt. So I'd have to use the stock firmware and convert just the 1900 to OpenWrt. But I would hope the improved specs for the 9600 would more than compensate for its other shortcomings.

Option 3
Switch to a mesh system and put a mesh unit in the cottage. This may or may not work with OpenWrt.