Play by Post vs Live play differences

Is that one of your Moves? :)
Which 'game'?
This Round Table? Sure, the signal tends to get lost as the 'recruitment' posts fall out of sight.

Do you mean your game with your friends? If you need more bodies, then recruit.
Is this not for the group you mentioned? Is this just you, me, and the archaeologist? (what is this Pasión de las Pasiones? Or Prime Time Adventures? That title Sounds like it:)
Two players is possibly the hardest number to run for, it has all the downsides of one player (one slip-up and everyone dies, lots of pressure on the players to be onscreen) without the main upside (intently personal and focused game); it also has all the downsides of three players (spotlight sharing, disagreements, exponential delays, the unavailability of 'singular tropes' like 'chosen one' or 'prophecies') with few of the upsides (viable alternate solutions and tie breakers, strong enough group to 'save' each other, varied perspectives).
Three is generally the easiest number to run for, and four is only 33% more to wrangle and devolves to three if one drops or is busy (three devolves to two, which is hard; two devolves to one, which puts games on hold).

If it is currently just the two of us, then recruiting one or two more seems wise. Personally I would first look to your group of friends and see if one of them wants to join (and I can step back if you have too much interest, I can still help, but don't have to be a full player). Playing with people you know and trust --as you have demonstrated above-- helps with the nerves and allows you to focus on learning the craft. Picking up a stranger is risky.

I like the players on this site, so you could do worse than pitching it to them.

Is there a PbtA PbP here with Public Forums you suggest skimming for how it handles the back and forth of move calling?

Not that I know of, unfortunately. But I have not read many of the games that I am not involved in. It can also be hard for an outsider to follow those back and forth's.

My PbP games have very few calls for moves, but you are welcome to look at any of the public ones and ask questions. But I don't think they will be the best examples.

It is only one instance and I am not sure the trigger is clear (mainly the player looked to me for what happens next) but one example of some of what we have been speaking about showed up in this recent post.

Note how one character had already taken preemptive action to protect themself, so I had the other character present make a roll. I tried to make it clear what the outcomes would be, that the hearing loss would be temporary (without defining how long that would be (till it got boring)) so the player would not stress too much, and I gave the player the option for what to roll (due to quirks of that game) with a few obvious suggestions (which also illustrate the type of thing we are looking for).