Stuck in a minimalist mindset and need enlightment on using polygons right

So my problem is, I am almost afraid of using to many pollys on my meshes, an example is modular walls:

When i create a normal flat wall, but want variation in how it looks so it dont get boring, I wanted to try vertex painting damage to some parts. But the thought of using let say 50 vertexes on one wall piece seems “wrong” in my Uncle Scrouge polygon head. Even when i create characters, I get a feeling of messing up when i cross the 3k poly barier.

So, can someone explain what i should aim for, and what I can do to make Game Ready assets that dont undershoot and looks stale and cheap, but dont overshoot and throws performance out the window?

Know this is a pretty “low level artist” qoustion even though ive been playing around with 3d on and off for some years, I just cant seem to shake this “Polyheavy anxiety” off.

Remember that adding 100 vertices is going to be far less data than making a large texture map, that’s one reason why it’s better for performance, besides also being very convenient.

Current platforms can handle characters 15k~100k polys just fine; all depends on the design budget, how many of these characters you want on screen at the same time.
In average games for ps4/xbone/pc characters will stand on the 35k polys range for the playable models and go up to 100k on cinematics, but for mmos or rts games where there’s too many units on screen at same time then even 1k per character may be too much.