Wifi drops when streaming horizon

Hold down the option key while you click on the Wi-Fi Icon on the MenuBar. You will geta screen similar to this:

what values do you show for PHY mode and Channel?

what RSSI or signal Strength?

What Transmit Rate?

and very important, how many other networks do you see?

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Your signal strength of -26 -95 = -69 is truly excellent.

Using 802.11n, you should get a base rate of about 50 Mbits/sec, and you are likely running three streams on it to get about 145 Mbits/sec, which is likely quite a bit faster than your connection to the Internet.

But you are using the very busy 2.4GHz band, which is where most of your neighbors routers will be, and is also shared with Bluetooth, microwave ovens, land-line portable phones, and USB-3 interference.

If you control three Routers, they should all be set to the SAME name, with the SAME encryption method and password (except your guest network which is not really separate). This will create your own Roaming Network, and your devices can hop from one Router to another to get the best connection under any conditions, including momentary bursts of interference. You should also give the 5Hz band the same name as well. It is only separately nameable to get you out of a few really obscure situations. For most Networks, it should have the same name.

Wi-Fi base stations: Setting up and configuring a roaming network (802.11 a/b/g/n) - Apple Support

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Duane pointed out that WiFi Explorer (US$15 with three-day free trial) can show you the distribution and competition of surrounding Networks:

(click the graphic to expand)

From the diagram, you can see the spectrum overlap of two Networks on Channel 1 (Red and Green) and two networks on Channel 6 (light blue and dark blue) and two networks on channel 11.

it illustrates how few clear channels may be available at 802.11b/g/n speeds many Routers try to use in the 2.4GHz band.

In the 5GHz band, a neighbor's network at channel 155 is way too low a signal to be useable by you.

Duane's Network (orange) has been manually shoe-horned between the usual bands and is using channel 5, but competing vigorously with the networks on both sides.

And my streaming issues are thus caused by the network(settings) and not by my Mac itself?

Neither of those.

Your streaming issues are caused by having WAY too many other Routers hogging the 2.4GHz band. When all is idle, you it appears you can get anything through no problem, because your signal is a lot stronger than their idle polling. But the instant any of those others tries to send data as well, your data will get clobbered. Then your effective speed will drop way off, and your Mac will [rightly] disconnect. Your Hardware is working as designed, but you are asking it to do too much.

Your signal is very strong. Do you have your Router right next to your computer? Is it on an Ethernet cable? If both are true, you would be better served by getting an Ethernet adapter for your computer and plugging directly in to Ethernet.

If you have a Router being used as an extender without an Ethernet connection, that means it uses half its bandwidth talking to another Router, and likely has to talk through that crowded mess on 2.4 GHZ.

The Router on the 5GHz band is right on top of a neighbor's Router. The easiest thing to fix that up a little is to set it to "Automatic" channel selection. Then when it powers up, it will choose a channel that is less busy, rather than trying to yell over a neighbor'd Router on the 5GHz band.

what band and what channel were you connected to?

based on the WiFi Explorer diagram you posted above, channel 13 (not always available) is the place to be in your network neighborhood for best throughput, and you should see far less disconnecting and other bad behavior.

Now that you have the more obvious issue of over-crowded airwaves under control, you may wish to run "Wireless diagnostics" from the Option-WiFI menu. It will examine your connection and give some general guidance.

When the box above shows, click ( Continue) and it will Monitor. Then leave that window open in the background, and go about your usual work. If something unusual happens, you will get an alert.