I only ever used it for 3D printing but FreeCAD apparantly also has a floor plan functionality. I found this video that might give you some insights on how it looks:
https://www.youtube.com/watch?v=WMk7pdnEnXM
When using FreeCAD for 3D printing, you don't necessarily have to add measures/constraints to everything, so I'd assume it's similar here.
I've used illustrator but ink scape (free) would also work. I just use basic shapes and just ignore the unit. Meaning that I consider a mm in the software to be an inch IRL. That way I can get everything into proportion in relation to each other. I use the text tool for labelling furniture and stuff, grouping, and align tools too. It's helped me tremendously.
I have used inkscape for this purpose and it can be effective. The display units can be changed in the preferences (inch, cm, etc) and basic shape dimensions input directly. You can input absolute position for shapes and nodes, but I didn't notice an easy way for relative position. They also have a path effect called "Measure Segments" for that functionality. FWIW, I later preferred blender, but I might try a dedicated tool like LibreCAD mentioned in another comment. They seem to have decent documentation and a wiki.
I always use gimp. Just define one pixel equals one millimeter, and then make all the furnitures as separate layers so you can move them around separately. Works great!
Are you referring to the measurement objects I mentioned in the draw.io portion?
It’s extra work that I find unnecessary if the walls already are set to the correct dimensions. I would like to be able to just turn on/off the visibility. And also not have to edit 2 objects for the same measurement if anything changes.