What X4 data has cloud backups?

[Raptor34]

I'm asking btw.
From what I understand there are several different pieces of data: save games, account, construction plans, custom starts, Timelines.

Saves:
This one is simple, it uses steam cloud saves.

Account:
Which I think also include venture data? Never used it before, but I think all these are basically linked to Egosoft.

Construction plans and custom starts:
Main reason I made this post. Do these also get backups in Steam cloud saves? Or do I need to manually back them up?
They aren't exactly bulky, but it's definitely annoying needing to redo my stations, especially those which aren't just 90 degree angles. And the HQ.
Incidentally, how does your custom budgeted start budget get updated and whether that data is also uploaded to Steam clouds?

Timelines:
I haven't started this yet because I watched someone play it and apparently there are cutscenes at the beginning that I don't have the time to sit down and appreciate, but I've seen roughly how it works.
So what I'm wondering is, how is your save data dealt with here? Does it just use your regular save slots? It's own save slots? Or is there just one master Timeline save that get's updated when you get back to the mission hub? I'm assuming you can't save mid-mission. But if you can, the logistics of it, so to speak, would be of interest.