At the signal level (1's and 0's) -- +5V and 0V (or 3.3V and 0V, 2.2V and 0V, xV and 0V where 'xV' is on and 0V is off) -- any computer interface, module or perhiperhal -- can be interfaced with any other one.

It's just a question of getting the voltage and the frequency and protocol correct -- so that electronic components will speak to other components along a signal path.

If one component cannot talk to another component -- because say, a given frequency is too high, or a given component is too slow -- then a proxy component which acts as an intermediator between high frequency and low(er) frequency sides may be used as a mediator; as an intercessor...

For example, let us suppose that I have a dumb terminal, the "dumbest" and slowest of all computing devices.

No memory to speak of -- except perhaps for a small amount of screen memory...

Now, if I want that dumb terminal to interface with USB, DRAM, LCD, Ethernet PHY, SATA, or PCIe -- I can use a Raspberry Pi to accomplish that (it can act as an intermediary, it can act as a proxy.)

Similarly, I can also use other electronic devices in lieu of the Raspberry Pi as the interface -- including but not limited to other computers, ASIC's, FPGA's, custom chips for handling signals, etc., etc.

That something wired together in such a manner is, or would be "unusable as a laptop" -- is a very subjective idea (unusable to whom exactly?) -- because properly engineered, it would indeed work, and would indeed be quite fast and useable...

By your argument, that component parts would be too slow, I would submit to you that:

Modern computer engineering is all about the speeds of various computer subsystems, and getting faster subsystems to work with slower ones.

These examples include (but are not limited to) the speed a computer's CPU vs. the speed of its memory (the cache hierarchy), Northbridge Vs. Southbridge, A Computer's Bus Vs. Slow Perhipherals, A CPU's speed vs. say, the speed of an older spinning mechanical hard drive, etc., etc.

Have a look at this table:

https://en.wikipedia.org/wiki/List_of_interface_bit_rates

The Internet (and the hardware that makes it up) itself is comprised of most, if not all of those devices, all of which have different rates of speed.

And yet, it all "magically" communicates...

Oftentimes a slower devices will need electronic proxies to communicate effectively with higher speed devices.

This principle is well understood in Electrical Engineering and amongst Electrical Engineers.

Not only that, but this very principle is enshrined in all computers -- even in the fastest laptop produced today...

The fastest laptop produced today has many subcomponents, many electronic subsystems, along which signals are travelling at different rates of speed -- some fast, some slow, some very slow -- and yet the whole system communicates and works, and is quite, yes, quite usuable...

That principle is enshrined in all computer engineering, and computers today.

Your uber-fast laptop, whichever make and model it is -- is proof, proof positive of it...

So, I appreciate your advice (I am sure it was given in Good Faith) -- but I feel that your advice only addresses the tip of the iceberg of the true scope of possibilites, the things that are possible when a more nuanced understanding is to be had...

The advice given limits the scope of what seemingly should be possible ("don't try it, it'll never work, or never work well") -- whereas the principle which I have submitted should expand the set of those possibilities ("it will work and will work well if the proper rules for engineering it are followed, with the proper understandings, with the proper first principles...")...