On Sandpiper, a 40' single engine displacement boat, the engine room is fairly spacious and headroom is tall enough for me to move around in a crouch. I am 6' 1", 175#. I can move around three sides of the boat and have easy access to all four sides and top of the Lehman. There is probably 3 to 4 feet between the engine and the fuel tanks on either side.
I can enter the engine room through a vertical door at the front of the engine room or stick my head in to do a quick engine check or access the fuel tank selector panel. At the back of salon, there is a hatch in the floor which I can hop down into the engine room. If I want more access, there are 4 large removable floor panels under the carpet.
I do engine and generator fluid checks and give the engine room an inspection before starting the engine. I close and open the two seacocks to make sure they open and close freely and inspect strainers for debris.
While under way, I do a hourly engine room visual inspection through the engine room door and on every other inspection, hop down into the engine room for a more thorough inspection. I check the temperature on critical components with a temp gun and look around for any leaks, unusual noises or anything amiss.
Sandpiper has more than adequate gauges and alarms but a hourly engine check has been part of my routine for over 35 years. I have caught issues before they get out of hand and before any indication from gauges or alarms.
I would not own a boat with a confining engine room or poor access. I spend too much time down there and comfort and the ability to move around is at the top of my list. I keep my weight down and maintain flexibility so I am able to continue as I get older. When I can't get into the engine room and move around easily is when I give up boating.