I thought the franchise was based on the made up technology called mass effect the species of the Milky Way galaxy used for long distance space faring. And since the technology came from reapers the only way i can see Andromeda working is the races coming from Milky Way bringing the mass relay tech with them. Im sorry, but a few asari and krogan crew mate dont make mass effect, its just fan service. "Mass Effect" does. You can say in another galaxy another kind of tech evolved to do the same thing but then only the title will be mass effect and you could call it any "random space shooter franchise" instead of it.
And yes, this is some kind of reboot/spin-off because the original team finished the story of Shepard and the Milky Way galaxy and they even stated this in the mass effect retrospective video long ago. The mystery behind the protheans and their mass effect technology is solved.
Yes it is a spin off, a different story in the same setting, that of mass effect.
Mass effect is used for alot more than just FTL travel using relays.
Mass effect fields are created through the use of element zero. Element zero can increase or decrease the mass content of space-time when subjected to an electrical current via dark energy. With a positive current, mass is increased. With a negative current, mass is decreased. The stronger the current, the greater the magnitude of the dark energy mass effect. In space, low-mass fields allow FTL travel and inexpensive surface-to-orbit transit. High-mass fields create artificial gravity and push space debris away from starships. In manufacturing, low-mass fields permit the creation of evenly-blended alloys, while high mass compaction creates dense, sturdy construction materials.
The military makes extensive use of mobility enhancing technologies, with mass effect-utilizing fighting vehiclesbeing standard front-line issue in most military forces. The Mako's small element zero core can reduce the vehicle's mass enough to allow a safe drop from the Normandy. Mass effect fields are also essential in the creation of shields to protect against enemy fire on the ground, and protect starships in planetary orbit or during space battles.
Many biotics can also use mass effect fields, which are biologically generated and controlled. This requires intensive training, and cybernetic implants, but can produce impressive offensive or defensive effects. Some biotics' talents are not strong enough to be offensively viable, but all biotics are sensitive to the presence of mass effect fields.
However, the use of mass effect fields creates static electrical charge. In starship drive cores, this charge must be grounded at regular intervals, either by touching a planet surface or interacting with a planet's geomagnetic field, to prevent the electricity discharging into the hull and causing catastrophic damage. For biotics, this manifests as an occasional static shock when they touch metal or other people. - From the wiki
So yes the mass effect fields that are the series namesake will be very present in the game as it is vital to much of the tech and abilties involved such as biotics, shields and the mako.
The reapers didn't invent mass effect fields anymore than we invented electricity, they just invented technology to use it via Dark energy (which like gravity and electromagnetism is meant to influence all matter), so its completely reasonable to think that species in other galaxies (if sufficiently advanced) could find their own ways of using it.