Wasn't it pretty separate in DA:I? I imagine it would be so here as well.
It was, but this seems a mix. But again, it seems less like Inquisition (I understand where the similarities lie) and more like Peace Walker. Inquisition's timed war table missions were static in that you didn't really
do much except pick one of three advisors to lead a behind-the-scenes mission. Real time required to pass depends on who you sent, as do often the mission outcomes and the reward. That's all it was.
This is a system cross compatible with the horde multiplayer, and they seem somewhat randomly generated. They pop up on the map and you have two ways to respond:
a) Send AI "Strike Teams" to complete the mission. Similarly to Inquisition they'll take X amount of time to complete, with rewards and results varying on performance. Difference to Inquisition is that your Strike Team is a game system you can upgrade, train, and customise, which is more like Peace Walker. Upgrade your troops, give them better equipment, send them on mission and they'll perform better.
or b) Jump into the mission
yourself with one of your multiplayer characters representing your strike team. You manually play it, and your rewards develop your strike team avatar. As they're co-op built, you can bring friends along with their own strike team characters and complete them that way.
To me this sounds pretty good. If you don't like the multiplayer component you can still have a multiplayer "character" and play it solo. And if you don't like that you can stick with your AI strike team that you still have to upgrade and develop.
How do they travel hundreds of lightyears between areas if there aren't mass relays?
If we want to go by the (largely nonsense) canon, ships were perfectly able to travel between solar systems with their mass drives. Traversing all the way across the galaxy was more problematic as it was resource intensive and time consuming. This is where relays came into play, as they gave direct links to various clusters.
Within a cluster, via one relay, you still had to manually pilot your way to various systems. You do this in ME2 and ME3 on the map, and ME1 just by selecting stuff.
For Mass Effect 4 you're only actually in
one cluster of the Andromeda galaxy: Helius Cluster. Since you'll probably be manually flying everywhere this isn't a big problem, as you were doing it anyway. It's more localised and confined, focusing on the solar systems and planets in a specific region of a galaxy rather than the
whole galaxy. Think like early exploration/settling in the Mass Effect universe, where you'd aggressive colonise nearby clusters and systems within before branching out too far.
This also gives them room for Mass Effect 5 and 6, if they exist. Helius Cluster covers Mass Effect 4, and the sequels move on to new clusters.