+1 for AxiDraw if you’re not into restoring a vintage machine. I’ve been impressed with the build quality of mine (it’s going on four years with no issues).
I’m also a fan of the Saxi driver software. Paired with a Raspberry Pi, it gives you a web-based interface to an AxiDraw so that you don’t have to physically connect your computer to the plotter.
The best pens are the cheap ballpoint ones, unless you already have rapidographers. I don't like using Sharpies because they fade out in the middle of the drawing and you have to plot at low speed.
For example, I ballpoint outlined the staircase piece (linked above) and then I manually filled it in with a Sharpie.
It works like old typewriters. You align the corners of the paper and then clamp it.
Compare that, at the time, to the top of line of a Gerber (or 3M) plotter that was the only one able to handle 12+ ft. It used an array of sensors that at runtime adjusted the clamping-wheels pressure to keep the paper/vinyl roll aligned.
It was around $15-18K, while my Ioline was ~$1,300.
So I have a 5' x 5' router table that I've modified to hold pens. I was using paint pens that require the nibs to be indented to get more paint to flow. They run out every 2-4 feet of line. It doesn't make great lines. Here is the machine re-loading a pen: https://www.instagram.com/p/CAD-tR1FU8J/
The "pens" i've made are a piece of delrin, with a 1/4" hole drilled down the middle and a piece of 1/4" F1 felt stuffed in there.
The first one is a perlin vector field plus a deformation. I haven't heard of those artists but I will look them up.
On the brush: That's a chinese calligraphy brush. I spent a bunch of time making a bearing holder to let the brush swivel freely. It didn't work. The brush is very, very hard to get to behave. A human will tilt it slightly in order to get the bristles to go in the right direction, but the CNC machine keeps everything completely orthogonal. Works for pens but not brushes.
Edit: Keith Peters' algorithmic stuff ( http://www.artfromcode.com/ ) does seem to share a lot of the same underlying techniques. Perlin flow fields and hex truchet tiles especially.
I snagged an HP7475a off a local buy and sell site recently for $60. Came with a serial-to-plotter cable (which I only realized after splicing that cable, working out the wiring, and finding it was already the cable I needed :( )
there were many manufacturers. the ones that seem to be higher quality were HP and Roland. alps made a tiny one that was repackaged for commodore, atari, etc. and there were a plethora of other manufacturers (graphtec, houston instruments, and so on)
check ebay for "pen plotter" but beware that many are quite large and shipping will be expensive.
i currently have a HP DXL 7575a (a large roller plotter) and a Roland DXY-1150 (small flatbed). the roland was shipped but the hp i had to pick up locally. roland still has the manual on the site for the 1150, but it required a wacky power supply that took some effort to find. for HP stuff make sure it has RS232 and not HP-IB interfaces or whatever wacky stuff. also, different plotters used different languages. Roland's RDGL and HP's HPGL were easy enough to implement directly from the documentation...
many of them don't work because various belts have died. my HP fired right up.
one ongoing concern is that pens are no longer made so you have to fight over scraps on ebay.
modern plotters:
get an axidraw. it is nice and lets you use standard pens.
In the commercial space, I think "wide format printers" have totally replaced plotters at this point. They're basically big ink jet printers, though usually a bit more sophisticated (often 6 or more inks, including variants like "matte black" and "photo black" and "gray"). The quality is very impressive, you can literally print posters or frameable photos on it if you have the right paper.
"XY plotters" are still around but seem to be very niche (emulating hand writing) or DIY/hobby stuff.
I remember being in an engineering office of some sort as a kid, fascinated by watching the multi-pen plotter [1] drawing some kind of technical drawing. It had a pen carousel to change colors, and a little robot gripper to hold it. Finding information on these (from the 2 minutes of searching I did) seems quite hard, so it seems like they probably went out of fashion before the internet was a thing.