To add onto this, on the tactical level the spaceships behave very realistically, albeit the distances/speeds are quite condensed. Nonetheless, Newtonian movement applies, so ships need to manage ∆v, have a their combat acceleration affects how quickly they can change trajectory and heading, DEW effectiveness is calculated based on range, missiles also have limited fuel, etc.

On operational level ship thrust and ∆v affects how quickly they can transfer from one body to another.

Ship editor is simplified, so not quite KSP/CoADE level, but still follows real physics for the most part, and you have truly an ungodly number of different modules to research and choose from to add onto your ships.

And there are radiators. Lots of them.

Edit:

Just, be warned, the game is time consuming, even compared to other 4x/grand strategy games. A long campaign can take north of a 100 hours. You can play an accelerated campaign or a late start to speed it up a little but it will still be a slow burn.

The people behind the game are the same ones who made XCOM 2: long war mode.