Currently, there is no scaling at all in the FGU playtest alpha. We do know that we will need to add basic UI scaling, similar to what is in current FG version.
The problem with adjustable text sizes is that every window and field is laid out by the ruleset developers to look a specific way; so it's not a simple solution to just scale text. The entire layout needs to be scaled, in order to preserve the layout of windows. There's no such thing as a responsive UI in FG (and that's a very complex thing we don't plan on addressing anytime soon). So, this means that macro-UI-scaling is the solution for the foreseeable future.
The one benefit in FGU is that the scaling will be on a per-object basis, which means that the text will be much clearer when scaling, since it will be drawn directly using TTFs at the final scaled size (instead of scaled after drawing like in current FG).
Regards,
JPG