Is stealth the best way to approach a timed objective?

I'm wondering if I'm misunderstanding the usefulness of stealth tactics in XCOM 2, specifically in missions where you start concealed, have to cross a map in a limited number of turns, and contend with multiple groups of hostiles hiding and patrolling everywhere (which FTR pretty much sums up every mission I've done so far).

If I have limited turns to get to the objective, that seems to imply at least one of my squaddies should make haste towards it, and I shouldnt get tied up in combat (Maybe I'm wrong about this, and there are different strategies for VIPs vs. bombs, crates, etc.).

But, inevitably I trigger alarms whenever I interact with the objective, and even if I get the objective successfully, I'm usually tasked with eliminating all hostiles, which are inconveniently all around the objective, and raining vengeance upon whatever poor soul I tasked with objective duty.

I've been scraping my way out of these missions, usually with at least one Gravely Wounded soldier, so I know they can be done. What I'm asking is what strategy should I be taking here, in general?

Should I be sneaky and avoid early conflict, preparing for an onslaught at the objective? (When I do this, I usually get overwhelmed by those onslaughts if I'm not perfectly positioned)

Or should I be taking out enemies as I encounter them, while still progressing towards the objective, so the mayhem is spread out a little more and the encounters are with smaller groups of enemies? (When I do this, I usually end up getting stalled by early combat and missing the objective, or sacrificing a squad member to get it done just in time).

No. XCOM 2 isn't supposed to be played as a stealth game, and, in fact, there's at least some evidence that the aliens will move towards your squad while the squad is concealed, and not just follow a patrol route like they do in most stealth games.

As you say, you generally have to eliminate all the enemies anyway, so there's no point in sneaking in/out like you might in Invisible Inc. or Dishonored 2. And by the time you get to the objective, from a gameplay point of view, you're in a worse position. Most missions start you off on the edge of a map, and then you move towards an objective, meaning that as you move along, unless you bypass enemy pods, you're unlikely to have enemy pods on more than two or (rarely) three sides of you, and will have some access to cover. If you do bypass enemy pods, you are likely to be surrounded and have no cover that's usable.

The point of concealment is to allow you to engage the first pod(s) you see in the manner of your choosing, and at least later in the game eliminate some number of enemies quickly. It also to some degree addresses one of the complaints about the first XCOM game, which was that when one of your soldiers exposed an enemy pod, they would get a free turn of movement to get to cover, and depending on which soldier exposed them, could end up putting your squad at a disadvantage. This still exists in XCOM 2, but for the first pod you encounter, your soldiers will be able to get to attack prior to the enemies moving to cover.

The only usefulness in stealth tactics is in your initial enemy engagement. As you get further into the game, you will be able to take a few enemies out in a calculated first strike while you are concealed. Instead of racing to the objective, I tried to keep my soldiers together. I always tried to end each turn in cover. Even when there was a timer, I was more successful when taking my time. I ended most turns in cover with overwatch. As the soldiers level up and you complete some research, the game becomes exponentially easier. I lost a lot of good men in the process, though.