Do you mean true Spot-and-Stalk? Or do you mean walking around and hoping to get a jump shot? There's a big difference between the two. Stalking an animal in a known location is far easier than just stalking space like I do still hunting.
I don't know if I am 'experienced' at boar, but I have hunted them, and I've hunted a LOT of other things up close and personal.
1) I am pretty good with irons. I still use a scoped rifle in the woods. The scope CHOICE is the difference, and by that I mean the field of view it makes available at low power. This nonsense of scopes who's magnification range starts at 3 or 4 (or higher) is absolute lunacy when it comes to shooting quickly in the brush.
In my opinion, a maximum of 2x should be considered acceptable as the low end of your chosen optic, if you intend to do this kind of thing.
The short rifle I use for that kinda thing wears a simple 2-7x33 Leupold. I lose maybe 5-10 minutes of late evening shooting, but it's plenty worth it for the light, handy optic.
It's not as fast as a dot (which are, incidentally, way faster than most irons), and is slower than I am with aperture irons, but not by much.
My FAVORITE mag range for short range is actually 1.5-6x. I consider short range anything from contact to about 400 yards, and on animals the size of coyotes, hogs, and deer, 6-7x is PLENTY of magnification for those range shots.
I have spent a lot of time teaching my muscles to bring my scopes to my eye on target and ready to roll. That's done in practice and drilling and dry-fire.
-Nate
Depends on the cover you are hunting. Around me when we drive them or spot and stalk thickets, my go to is a open sighted 45/70. If the cover is thin and you can spot them 100+ yds away, Id have a scope. Hogs hold tight in cover and I've shot them as close as 10 yards. Scope at 10yds is not useful.
IMO, the only reason to use iron sights would be for nostalgia or to add additional challenge. A low power scope or a red dot are both better options if you simply want to put some pork on the ground.
I used a scope set on 3x to drop a pig running flat out at about 7 yards without any problem. Considering the size, or lack thereof, of that pig, the scope was very useful.
You don't understand the term "thicket".