MBP M1 not using the available bandwidth

You have made a connection in the interference prone and typically VERY busy 2.4 GHz band. your Router is transmitting using 802.11n rules, which are old, bordering on antique, Issued in 2003, replaced in 2009 with 802.11ac and again in 2014 with 802.11ax).

It is very surprising you have not connected in the 5 GHz band instead, unless your Router is so old it does not have the 5 GHz band. If you are in an apartment building, that will NOT be good enough.

You have good signal strength at -59 dB, where about -40 is 'right next to the router' and -65 is 'searching for new network to join'. What is NOT good is noise at -75 db (should be more like -95 dB) which indicates active interference, likely from other Router nearby, microwave ovens, baby monitors, or portable landline telephone and similar sources.

You are using 16 pattern per signaling interval, likely because the next step up, which uses 64 patterns per signaling interval, is not sustainable with this interference level. Both antennas in your Mac are working together.

I do not think you have a hardware problem.

if you post the make&model of your Router, readers can do some research and see if it supports 5 GHz band as well.

Poisoning Internet performance:

By far the easiest way to cause poor performance, instability, overheating and crashing is to install ANY third-party speeder-uppers, Cleaners, Optimizers, or Virus scanners. or a VPN that you installed yourself.

The idea that a third party, with no special knowledge of the inner workings of MacOS, can somehow find a simple way to protect your computer — that is not already being done by MacOS itself — suggests that the MacOS developers are somehow "holding out on you". That is absurd.

You should remove any and all (other than Apple built-in) virus scanners, speeder uppers, optimizers, cleaners, App deleters or VPN packages you installed yourself, or anything of that ilk.

Third-party file Sync-ers such as DropBox, BackBlaze, OneDrive, or GoogleDrive can ruin performance, but are not inherently dangerous.

Effective defenses against malware and ot… - Apple Community

Effective defenses against malware and ot… - Apple Community

when Wi-Fi was introduced, channel numbering was based on very narrow channel width. Today's uses mean that the spectrum used spans from the nominal channel, and two channels up and two channels down. That leaves only THRRE main channels in the 2.4 GHz band, uses you fiddle around trying to squeze in between others and hope you don't get your data clobbered all the time:

graphic from wikipedia.

the center chart is the one that applies here.

using an inexpensive spectrum utility like WiFi explorer, a messy (nee nearly dysfunctional) network can look like this:

The Mac isn't throttling. Your ISP provides you with a maximum obtainable speed; the most you can ever expect under perfect, laboratory, ideal conditions. Ideal conditions you will never experience. Overheads reduce the max possible to some smaller percentage of the maximum provided plan speed.

And, there is net congestion to consider, busy servers, time of day signal dilution and a multitude of other things that attenuate your signal

What are signal "overheads": https://www.linkedin.com/pulse/economics-computer-network-overheads-mohan-bvk

In today's environment, 20 MBps is abysmally slow.

I use Verizon FIOS, which is a fiber-optic connection to the home. Of the enormous potential bandwidth, I have contracted for modest connections speeds of 25/25 M bits/sec.

From time-to-time, I have found my internet connection seemed to slow to a crawl, So I contacted the vendor for assistance.

Their standard procedure does a reset of all their devices. When completed, I found the speed improved. The technician does not know why it is any better. But I do.

The IP address assigned to THEIR part of the network had changed. In other words, they made different internal connections through different Routers at their end to balance the loads differently, which improved my day-to-day results.

if you want to encourage connection to the 5 GHZ band:

• turn off WiFi, wait a quarter minute, then turn it back on again. It is supposed to make the "best" connection.

• you could manually split your network, giving each band a distinctive name, and manually connect to the one you desire. NB> this is a step backward from the growing trend of giving all bands the SAME name and having your Mac and your Router cooperate on choosing the "best" connection or re-connection for the moment.

Great, but first we have to make those gratuitous checks, because otherwise the detailed ongoing investigation becomes impossibly difficult.

Hold down the Option key while you click on the Wi-Fi Icon on the menubar. You get a snapshot of current operation like this older one. transcribe or post a screenshot:

.

Because the 2.4 GHz band is usually more crowded, a lot of users will connect on the 5 GHz band by default, where channels can be wider. Lower frequencies carry farther, so 2.4 GHz carries farther. On 2.4 GHz, you also may find Wi-Fi-capable Printers and Internet of things devices, which may appear as additional Routers.

If you really do live "in the woods" as I do, with neighbors too far away to interfere, you could consider changing your Router settings to use a 40 MHz channel on the 2.4 GHz band. (This would HOG the ENTIRE 2.4 GHz band for your one Router, and knock your neighbors Routers off the air, if they were close by.) that may or may not improve the transmit rate.

Are all the files involved stored on your Apple-silicon Mac Boot drive? Or are some stored on different drive?

it is possible your connection on the 2.4 GHz band using older 802.11n, which does not really benefit or speed up much with 802.11 ac or ax. Sometimes that just reports as 802.11n, even if the Router is more capable. (Possible false alarm, if you know your Router is more modern, ignore it.)

Read your Internet Speed Test numbers with extreme caution. Most Internet connections are measured in bits(small b) per second. If you are transmitting at 78 M bits/sec, you can easily attain 20 M bits sec, about a quarter of your local transmit bandwidth.

What have have expanded is you expectations.

Because of what the ISPs call "overheads" you will seldom get the speed you've purchased. At any given time, you'll be lucky to get 70%. During time of high internet usage, all users on the line not just you, it may drop to 40-50% or less.

https://www.howtogeek.com/165321/why-you-probably-arent-getting-the-internet-speeds-youre-paying-for-and-how-to-tell/

Now days 20 Mbps is dismally slow and gives you essentially no "wiggle" room. We've just been given a "no cost" upgrade from 600 Mbps to 1000 mbps and we still suffer from the same speed problems. But for us the slowdown is hardly noticeable.

If you have serious uses of the internet, I suggest you investigate a higher bandwidth plan.