These are some questions which are not that easy to answer, because depends on your type of game.
But you can answer the questions yourself:
If your game has 100s of game entities and every entity has to do a full pathscan to find the next waypoint, when the entity arives at a new node ... with this method dynamics of units can be taken into account, BUT this will kill your FPS.

If your game has only a few units this method should be no bigger problem for the FPS.
It also depends on the number of nodes - to find a path through 10000(100*100) nodes can take much longer than calculating a path through 1000(10*10) nodes.

What kind of algorithm you will use, is also an important question. For some applications a Brute-Force-Algorithm could be much faster than for example A*, for other apps A* is the one and only. Sometimes simple obstacle-avoidance could solve problems, too.

All depends on your type of game.

I hope this will help you a little bit.

Bye G.S.