Question The best wifi 6 router for under 100 dollars??

None of the above would be my recommendation even though I am surprised these device have gotten so inexpensive.

The short answer is going to be buy wifi6e BUT you likely will need to wait both for the price to drop and for more end devices to have support.

So wifi6 has been pretty much a disappointment. In some cases people can get it to run faster than older 802.11ac (wifi5) but a huge number of people see little or no difference.
The reason for this is the only way to get the fast speed on wifi6 is to use 160mhz radio bands. The problem is there is no band that wide on the 5g radio band. They must use space used for things like weather radar and if they detect this radar they must stop using the radio band.
Because of the added cost and complexity of this many devices only support 80mhz which is the same as wifi5 and you lose the key reason wifi6 is faster. In addition you are overlapping pretty much every other person using 5ghz radio so you get lots of interference.

At least 1 of the routers you list supports 160mhz BUT that is only half the connection. It is very rare for a end device to support 160mhz. Almost all portable devices (ie cell phones) only support 80mhz because of complexity of avoiding other signals. Both the router and the end device must support 160mhz to be able to use it.
Some of the other routers you list only use 80mhz but they try to "fix" this by using 4x4 mimo. Again almost no end device has more than 2 antenna so the feature will be unused. This issue with MIMO is very common even with wifi5. You can buy a fancy router but end device because they want to reduce size and conserve battery do not have these feature. You can buy fancy wifi nic cards for a desktop machine but for desktops you are much better off using a ethernet cable if there is any way to accomplish that.

Until we see things like cell phones and tablets get support for wifi6e it really doesn't pay to upgrade routers past wifi5.