Basically, how fast you can transfer over wireless is determined by:

1) how effectively you can pack data into a channel, determined by the modulation scheme.

In your wifi properties, you can see the modulation scheme used as 'MCS index'. You will see an integer between 1 and 11, the higher, the better. This is negotiated between client and AP, depending on the signal strength (antennas, number of walls/wall material between them, etc). With wifi 5, it is realistic to have MCS 8 or 9, if your client and AP are in the same room.

2) how wide is your channel - the "basic" is 20 MHz wide, newer standards can combine multiples, into 40, 80, 160 MHz wide one. Wifi 7 will bring 320 MHz wide channels.

2,4 GHz band has only 3 non-overlapping 20 MHz wide channels available. If you use more than one, your neighbors will hate you. The situation is better with 5 GHz band, unless you run into the DFS (radar detection), then you can have intermittent outages. This is improved by Wifi 6e which brings more channels in the 6 GHz band, but the client and AP support is not there yet. Currently, running an 80 MHz wide channel bellow DFS frequencies is probably the best.

3) how many many simultaneous streams you are able to transmit/receive - MIMO (one client using multiple streams), MU-MIMO (multiple users using multiple streams, so they do not stomp on each other and sidestep next point).

Most clients are capable of 2x2 MIMO, older Apple MBPs (pre-2019, -ac based) are capable of 3x3. Most APs are also 2x2. The nicer APs can do 4x4 MIMO, some gamer APs by companies like ASUS can do 8x8.

4) how effectively can multiple clients share the same channel.

Here the problem is, that once an older client connects, it is downgrade for all clients, they must be compatible. If you can, keep your 2,4 GHz network -n and higher, and 5 GHz -ac or higher.

Once you will be able to have a band -ax only, you could theoretically be able to use OFDMA, which does improve the performance for multiple clients.

You can have a look at mcsindex.com: pick the modulation scheme (row), number of MIMO streams (group of rows), how wide is your channel (column) and OFDM/OFDMA (group of columns) and there you can see the theoretical bandwidth. Note, that it is a shared bandwidth, for all clients.

There are some minor points:

5) if you have IPTV or another application that uses multicast, do not run it over wifi! Multicast by definition does not have ACK, so what can AP do to ensure every subscribed client gets the data? Slow everything down, for everyone. So do not let it do it.

6) multiple SSID - possible, but do not overdo it; they also have performance impact (the SSID advertising takes time, at the slowest/most compatible rate allowed; the more of them, the more time it takes). Ubiqiti limits them to 4 per radio.

7) at higher frequencies, you won't have a such range than at lower ones. This is both good and bad thing. The bad, obviously, that your range is lower. The good is, that the range of your neighbors is also lower, so you could use the same channel without disturbing each other.

8) It does not help to crank the tx power to the max. The clients may receive, but when they answer, the answer could never arrive. Clients do not have antennas or tx power like APs do. Use the tx power reasonably; if you have multiple APs in your house, adjust it so clients will let go the weaker signal and connect to the stronger one (which AP connect to is fully managed by clients, unfortunately, and they often prefer to stick to the one they are already connected, even if different one with stronger signal is available. At most, some APs can kick the client once the signal is below threshold you specify).

9) some cheap dual-band APs have only single radio, capable of transmitting at both frequencies. Not at the same time, obviously, they time share. Make sure your APs have separate radios for each band they support.

10) some APs do support roaming (802.11-k/r/v); for home (or WPAx-Personal) that's not that important. It is enough if your SSIDs are named the same and have the same password. Roaming support helps with WPAx-Enterprise, which is much more heavy-weight.

If I was revamping my home setup today, I would pick something from Ubiquiti that can do 4x4 MIMO, probably U6 Pro; if the top speed was not really an issue or there would not be two users trying do download the internets, then probably U6 Lite (I'm running nanoHD today, and even that can utilize the 1 Gbit ethernet uplink to its full capacity). Mikrotik is supposedly also working on Wifi 6, but they have nothing available right now. If you have a better budget, then there are brands like Ruckus. The choice is affected by about how big is your home, what is the disposition, what materials are used, where do you want to place your APs and how you need, are your neighbors noisy (in wifi), what you expect from the wifi and what is your budget.

So I hope that this helps you for a start.