@Charmaylarg Dufrain Check out
Children of a Dead Earth or 'Everything you wanted to know about space combat but were afraid to ask'.
Everything is accurate down to the Physics, materials science, and the Voltage going to your coilguns (or rail guns, you can custom-design your weapon down to the material in the barrel, the number of coils in the gun, the capacitors attached, what cooling pump you use, etc.)
The game starts out as an easy Kerbal Space Program and ends up as a very hard Kerbal Space Program.
If you want even more specifics check out
Atomic Rockets and
Rocketpunk Manifesto. Atomic Rockets hurts the eyes to look at but it is overflowing with useful information. Rocketpunk is more aimed at people like you who want to try and apply some logic to their RP setting.
----
Distilling all of this down is hard. Yes things in space would be made very lightweight but at the same time we have powerful engines and can make 'lightweight' things very strong. We also have the DRv3 problem where larger objects are inherently stronger and better armored. For example a large transport plane would be better armored than a tank.
But yes: 'Things are super-deadly in space'
But also: 'There are a lot of qualifications and specifics to that which can make killing something very difficult'