PERSONALLY I use Loctite all the time. Use the blue stuff on anything that even might vibrate loose. Intakes-yes, headbolts-NO. I use it on rod bolts, sidecover bolts even carb mixture screws that tend to move. Use the red stuff on any stud or like me on exhaust bolts. If you need to take the bolts/studs out just heat a little with a propane torch and they come out no problem. I have used this stuff for years and years and would rather use it than not. Better safe than sorry-trust me.
In the first pict I would use it on the clutch bolt but the secondary looks good to go with that locking setup already installed. The second pict I can't tell what it is. Intake bolts absolutely. Personally just think about it-IF you use the blue stuff even if it isn't torgued super tight at least however tight/loose it is it won't change. I personally build small engines/equipment every day and I swear by the stuff. If you want it to STAY TOGETHER use it-if you are going to take it apart all the time than don't. I use the "red death" loctite on exhaust's all the time-they don't blow gaskets because they don't come loose. Anyone that knows-has seen me knows that I have the physical ability to tighten bolts to their limit but it's not about that-it's about vibration and the loctite cures that. Again IF you don't want it coming loose on it's own just use it.
