So here's my crack pot "theory" of FTL travel in a nutshell. Any relationship to current physics is purely coincidental. If you see one let me know! I dig that stuff.
Stars generate membranes in a parallel space (hyperspace or jump space). The branes are generated by nuclear reactions or similar energetic processes. The number of branes generated his related to the amount of energy generated. Small dim stars have one brane, a star like Sol has three.
Gravitational collapse can maintain membranes for a while. Pulsars, black holes, and white dwarfs may have membranes depending on how recently they exploded/collapsed. Brown dwarfs may have branes but I made this set up complicated enough.
Anyway, branes have levels of energy designating where they form around their stars. Up to four branes is stable. they form at the same distances. Other stars, objects in the system, and solar variance may distort the branes but aside from plot devices, these are minor.
M-Drives tap into the energy that maintains the branes -to a point. They work by attracting or repelling the system's star.Of course, unless you have a huge ship, the ship does the moving and not the star. They have a top speed because at some point the inefficiencies of any engine overcome the energy you put into it and merely generate waste heat.
FTL travel requires very little energy. In fact the normal energy use for a power plant is .01Ms
(Ms= Mass of the ship). thrusting in a system does require energy. .1 Ms for an week's thrust at one gee. Drives have a top speed based on their maneuver rating
M-1 1 gee 48 hr/AU (900 KPS)
M-2 1 gee 24 hr/AU (1800 KPS)
M-3 1 gee 16 hr/AU (2700 KPS)
M-4 1 gee 12 hr/AU (3600 KPS)
M-5 1 gee 10 hr/AU (4500 KPS)
M-5 1 gee 8 hr/AU (5400 KPS)
Note that this changes almostt nothing in combat. Few fights will last anywhere near long enough for a ship to reach its top speed or be started near top speed as this generally takes 24 hours at its full thrust.
Also note a 6 gee boost for 24 hours consumes 6 days of fuel. Also note you have to slow down, requiring an equal amount of propellant. No doubt players of Triplanetary are grinning right now.
Diagram above shows a star system with all four branes. A ship with a maneuver-1 drive can cross from one box to an adjacent one in twenty four hours. It's vaguely related to node maps. A jump point will cover a box or several depending on how close and bright the stars are. It got a lot harder to detect a ship jumping into a system. However, ships now take a while to get somewhere so you will spot them eventually.
For the people worried about weapons of mass destruction, assuming a g gee drive mounted on a greatly altered Scout/Courier and assuming the actual mass is about 500 tons (somewhere between aircraft density and metal hulled water vessels) and it actually hits a planet, we have a 1.7 gigaton boom! Hardly worth it to lose an able vessel.
The ship will be moving at 5400 KPS. That is (5400*1000/10.000) 540 range bands in combat scale. Now that is impressive, but again, missiles in CE will move 40 bands. If an incoming projectile is detected 2 light seconds out that gives the defenders a chance to fire missiles, one round. Not fractions of a second. And a 50 kilo missile would impact the incoming Scout with the force of .17 kilotons. that's one missile. that should divert (if not destroy) our would be dino-cidal maniacs.
Not every world will have such defenses. They will have little reason to waste a Scout ship on them. Conventional weapons will work well enough and not make every fleet in the vicinity come gunning for you.
In the event of an actual war well that is a lot of trouble to go through when regular nukes are way simpler to employ.
It now takes a while to crawl through star systems. Branes and jump points may be a ways off from the main world. There will be fueling stops, spaceports and infrastructure and encounters of every sort. Now instead of flying to 100 diameters from the mainworld you need to get to the jump point you want. There ie some wiggle room here. Ships can fly into a system, haggle by comm over freight and have a cargo or freight lined up by the time they land.
As for transition between stars ... instant transitions pose questions. Communication in an interstellar empire now becomes faster than travel. Ships have to travel between the jump points. A relay system of ships however, could just keep 'porting between two systems, beaming important messages to a ship doing likewise at another jump point will take only hours or minutes. Instead of the Age of Sail, communications move into the Age of Steam. Ships plod along but telegraph systems can notify far-flung posts and issue orders much more quickly. Naughty characters have to step lightly. They no longer can outrun their reputations. A system hooked up with comms will know everything about them, warrants, like on social media etc.