How safe is it to mount a TV tight to the wall with steel studs?
If the TV will be on a pivot arm the answer is absolutely not.  If it will be tight to the wall, as you say, and generally nobody will be physically handling the TV (tilting or moving, e.g. to plug in game consoles or whatever) then it can be quite safe especially if you use several (4?) toggle bolts along the top edge of the bracket.  You don't need them on the bottom edge, use self-drilling drywall plugs.
You don't need a special bit to drill a metal stud, a good wood bit will do it and if you know how to use a toggle bolt you just use it the same way in the stud as you would in the drywall ... but you get a better result.
Why don't you go buy a sharp new drill bit and a metal stud to practice on?  They cost like $4.  If you live somewhere with metal studs it'll be the best $4 you ever spend.  The only special trick you might want to consider is getting the toggle flat against the inside of the stud wall ... you have to spin it and feel that it's not half on the outside and half on the inside of the channel.   You'll need all of 2 minutes of practice to master this.
Here is what the toggle will look like from the back, with drywall and a metal stud and an appropriate hole having been drilled for the toggle.  The model you mention would require a smaller hole.  And you can see here what I mean about spinning the toggle so it rests flat on the metal joist.