actually for router i suggest mikrotik, for wifi ubiquiti. The reason is that mikrotik is a far better router and ubiquiti calls their fanbase fanatical alongside with other dodgy things in their company politics (shareholder stuff).

reading the needs, ASUS routers are actually good, but you have to update the firmware, the best way to test is to connect via wifi AC and ping the wifi router itself. Currently even my asus routers are giving me issues on wifi and the best ping i get is 2ms, with the tplink given by tm, i get 1ms or less on wifi.

If you have the tp link given by tm, use that for wifi and use mikrotik as your router, you will get the best experience this way. Otherwise consider getting mikrotik for wifi as for mikrotik, as long as you have sufficient ram and CPU, it wont matter how many users you have whereas with ubiquiti can be buggy for many numbers of users depending on model though.

The problem here isnt the internet speed, because even an old single core MIPS router can do 1Gb/s using hardware acceleration, the question here is on wifi and i know by heart that even consumer gear can handle a decent number of clients on wifi, it all boils down to how the wifi router handles wifi clients, either through software or the wifi chip. This is actually where some high end consumer routers are ill equipped because the wifi chip is router through the switch chip which means that the wifi chip is handling the clients limiting the number of wifi clients. Mikrotik puts the burden of handling wifi clients on software, and so do some ubiquiti wifi APs. At a low price point, going with either of those 2 brands for wifi is a good choice for hundreds of clients. MU-MIMO can also be an advantage here too.

As far as speed goes, my router will do 10Gb/s software NAT with firewall and QoS without issues but i am also on 100Mb/s unifi. With routers like mikrotik theres no need to spend so much money on a high speed router as you get the same features regardless of price, which is different with ubiquiti. I dont usually recommend ubiquiti after seeing their booklets on trying to get investors, shady business practices and so on.

If you want serious enterprise stuff i'd recommend you go with a self built x86 based router with the right OS choice for the job (linux server or purpose based OS like pfsense) coupled with actual enterprise APs and not look at either mikrotik or ubiquiti however ISPs do use mikrotik at their exchanges because their price/performance cant be beat not even by ubiquiti as ubiquiti's speed claims are unreliable for the kind of customers that use them.