1.) are the enemies visible or invisible - it's always tedious to fight invisible enemies and find secret rooms - that's why I always prefer visible enemies on games that have secret rooms .
You'll be happy to know it has visible enemies (except on the worldmap but there won't be secret rooms there

).
2.) the rooms can be found just by bumping into walls and places like the Tale of a common man or you have to actually click on the wall to enter the room ? So I know how I would play it in regards to finding them
There's usually a subtle hint to indicate them.
I'm still in the process of making the game so can't give a definite answer but more likely you bump into them (no need to click). Of course it depends of the nature of the SR, some might require clicking, if that justifies it.