I doubt that you could tighten the studs even with access to the head side of it, there is no socket for a Hex wrench, and the head isn't hexagonal, so no way to tighten it down, and it isn't threaded into the hole in the control arm, it's pressed in, cutting spline grooves as it is pressed home.
They are just like wheel lug nut studs, the head is flat and smooth, and there is a spline on the neck of the bolt just below the head.
The hole they are pressed into is undersized, which results in what we call an "Interference fit" in machinist's lingo.
The leading edge of the spline is beveled a bit, so it starts into the hole (under a whole lot of pressure, usually tons per square inch) easy, then the splines, which are hardened , cut grooves into the walls of the hole.
By the time the head bottoms out against the metal around the hole, the splines are done cutting grooves, and the stud is locked in pretty tight, both against being pushed straight back out, and against rotating.
If you don't tighten the nuts down on the studs too tight (look up the torque specifications, and use a torque wrench, or tell me the diameter of the studs and I will tell you the torque specs for it) they should hold as is.
If they are tack welded in, and a stud ever breaks, gets bent, or gets mangled to the point that you can't clean up the threads on it with a re-threading die of the proper diameter and pitch, you will have to replace the control arm most likely.
Although with careful grinding with a die grinder or Dremel®, I suppose it might be possible to grind away the tack welds and then press out the stud, and put a new one in.
But remember when you press in that new stud, it will either have to be oversized in the area of the splines to cut a new set of grooves, or you will have to be very careful to get the splines aligned between the grooves the original stud cut, so that the new stud's splines can cut their own grooves.
That latter situation is not optimal by the way, as the amount of metal around each of the new grooves is less than what it would be with a fresh hole, one that had never had a stud pressed into it.
Here's a picture of a stud where you can see the splines I am talking about.