Absolutely, any X Series pedal should work with any 12A*7 tube, 6021, 5751, etc. (let me know if you're adventurous and are tempted to try other dual triodes, I can let you know if others will work).
So that's a big question, I'll try to tackle it as simply as possible:
Phaser, flanger, and chorus are all very similar in that they take the original sound, delay it slightly and mix it back in, with various filters, phase modulations, etc. These can all be done with analog, and these days a Bucket Brigade Device (BBD) is regarded as the most "pure" analog way of doing it. That being said designing around a BBD is not very simple, and while getting one analog device can do all of them is theoretically possible, the chances of having one circuit that does all of them
well would be extremely difficult, which is why you don't really see a lot of cool analog options out there.
Robot Butterfly is a digital pedal (analog dry path obviously, but the effects are 100% digital), and it uses the now ubiquitous FV-1 processor, which is generally the go-to for digital effects (especially time-based effects) for both hobbyists and professionals. I can't even begin to explain how much easier it is to do things digitally, and with chips like the FV-1 we can even make them sound good! I used to make a pedal I called "Black Mirror," which was essentially a clone of the original Deluxe Memory Man, and it was my go-to delay for sweet chorus-y delayed sounds. But analog has its shortcomings, and now I use an Echosaurus on my board (also an FV-1 based pedal) because it has more options and is 8000% easier to build.
Sorry for the big long rant, I hope there was a coherent answer to your question in there somewhere
But Dr. Wattson also doesn't have an LED bar, so maybe not that valid of an excuse.
