The word "tri band" has a couple meaning now days. The older one when you look at mesh units is they added a second 5ghz radio. This is generally used as a dedicated backhaul between the main router and the remote mesh units.
The newer use mean it also has a 6ghz radio that is used on wifi6e.
If your end devices also do not support wifi6e then that extra radio chip is unused.
The so called tri-band mesh units attempt to use the extra radio to avoid having the user data transmitted on the same radio and the backhaul. This designed used by simpler mesh systems cuts the bandwidth in at least 1/2. The problem with the concept of using 2 5ghz radio is it does not magically increase the amount of radio bandwidth there is. The 5ghz radio band is massively over crowded. There are really only 2 80mhz blocks you can use unrestricted and these fancy mesh unit attempt to use both. That means any other neighbor will overlap at least one if not both your signals. If they attempt to use 160mhz radio bands (ie wifi6) you now have 2 radio blocks that have to deal with interference with things like weather radar.
Although I have not seen them maybe mesh unit that have 2 6ghz radios might work better because there is much more bandwidth on the 6ghz radio band.
In any case as kanewolf recommended I would try to use a ethernet cable to hook up the remote units. Any kind of mesh systems tends to not work even close to what they claim thank