Electronic – Confused about KVL / KCL / ohm’s law

Whichever gives an easy set of equations. If you are doing resistor networks, count if there are more loops or more nodes. KVL if there are more loops, KCL if there are more nodes.

In more advanced circuits, like transistors, there is normally a very specific mode that lends itself to your problem space.

This answer is probably inherently displeasing to the feeling of natural order for some :-) :

A law of nature is simply a statement of observed results under defined conditions.

Ohms law is essentially a statement that the ratio of the two two variables V & I is typically observed to remain approximately constant as the variables vary.

It is arguably saying the opposite of what it may seem - ie not so much
"R is the ratio between ..." but
it is more "if the ratio between V & I is constant then we call this constant resistance" and "this approximates typical behaviour of a significant proportion of real world products".

At any given moment R IS the ratio between V and I. If this ratio has changed then R has changed. So V/I never changes for specific values of V & I with all other conditions held constant, whereas dV/dI typically does change in the real world.

So R = V/I is an accurate statement
R = dV/dI is usually an approximation and
where it all falls apart it just means that the observation does not apply under thos e conditions.

That's woolier than I'd like but seems to convey what I'm trying to say. I hope :-).