Two best approach discs I've ever used or tried BY FAR are the Kastaplast Berg and Discmania Tactic. They both completely changed approaches for me and shaved strokes off my game. Especially the Berg. Not sure you can find a better approach disc than a Berg. Once you get used to it's somewhat different shape/feel and really learn it, it's hands down THE BEST. You can make almost any shot with it from 200' and in. And I even putt with it often and it's just about as good as my favorite main putter (K3 Reko). FH, BH, hyzer, anhyzer, dead straight, super soft landing, no roll, no ground play, low glide, YOU control what shot you want with it, and it will do them all!
The main reason being is that they are so easy to throw and so consistent. Which has not only helped me park approach shots on par 4's or 5's, but more importantly save par from a bad drive. Knowing I have those discs in my bag, gives me so much confidence to know I can probably save par from a horrible or unlucky tee shot. Have a SUPER delicate downhill run away approach? Berg! Super touchy side lie basket? Berg! If you throw it right, it WILL stick to the ground like velcro and always leave you a short putt.
BH AND FH! Both are incredible for either. And I have both in a few different plastics for different courses or shots: Berg in K2 and K3 hard, and Tactic in soft and hard. The Bergs are more dead straight to slightly O/S, while the Tactic's are definitely O/S in both plastics. Also the Tactic is super flat top, which I love, as well as the A3/A4. While the different plastics of the Berg are more curved. The K3 hard being the flattest top of the bunch.
K1 plastic is like the most ultra premium plastic you can buy on the market! It's like the durability of the best Champ or C Line, but has more grip and just a tiny bit more flex. But is super stable and lasts FOREVER. Also comes out of your hand SO CLEAN. Has a nice slick sheen to it, but somehow still allows you to grip it so well.
K2 is basically the same as K1 but softer and more flexible. Not quite ultra squishy taco plastic soft, but not too far away. So it's PERFECT for an approach disc. Comes out of your hand SUPER CLEAN. And sticks to the ground like velcro.
K3 is like a really high end base plastic. Kind of feels like Exo Soft from Discmania. Has that low end plastic base feel, but has an interesting chalky but somehow grippy like feel to the exterior. Beats in much faster and gets nicks quicker, making it amazing for approaches and grabbing chains when putting!
When approaching a tough basket that has hard ground or where the disc could roll away, I always use the K2 Berg. It is soft and gummy, so it sticks to the ground really well and usually doesn't roll away because of how it lands. Whereas I use the Tactic on longer approaches and/or when the ground isn't hard (maybe a grass landing) or where the ground isn't going to possibly make the disc roll away. As it lands usually on a little more of a hyzer angle and has more potential to roll. But if you are good at nose up anyhzer approaches, then it won't matter. I'm just not that good yet at those, so that's why I carry 2-3 approach discs.
The Tactic is basically Discmania's version of a Zone or Harp. So you could add those two discs into the mix as well from what I hear they are almost identical.
Another really good approach disc that I would put in this grouping is the Prodigy A series, specifically the A3 and A4. To me, they play a little bit longer than both the Berg and Tactic, but in reality, they all probably fly about the same distance give or take 20/50'. It's just that I use the A4 more for throwing, then for approaches. It has a very interesting thin profile, flattish top and very blocky flat unique wing shape. And on the underside of it, the overall profile is flat. So when you throw it flat or low, it really gets a lot of skip or ground play. Which is not ideal for an approach. At first it was a little odd, but INSTANLTY fell in love with how it feels and throws coming out of my hand for 200-250' shots, and even more so for odd escape shots or FH's. It REALLY shines FH because of it's unique shape and profile.
The only problem for me with it for approaches is that I can't throw that nice little soft nose up anyhzer approach shot yet (still working on that and trying to get consistent) that just dies where it lands. So it always comes in hot and on a hyzer angle. So it skips and has a lot of ground play. Which for certain shots is amazing and I keep it in my bag just for such shots. Low ceiling or skip shots are amazing with it. Same for the A3, but it has even more hook/fade than the A4 and isn't as long for me. But because it's so thin and flat, it really gets a lot of ground play when thrown medium to hard and flat or low. So it comes in handy sometimes and saves my butt, where I would not be able to do that with the Tactic or Berg. Those discs have the traditional thin wing profile (which means when they land, they grab more), while the A3/A4 have this unique flat blocky wing shape that really makes it skid off the ground really easy when thrown a certain way.
But if you can throw them with that sweet little soft nose up anhyzer flight path, their absolutely money. And if/when I learn to throw that shot, I'll probably only play with an A4 and Berg at that point. Kevin Jones game was transformed he said when he finally made the switch over to the A3 discs! So I'd add it to your list and pick up a few A3/A4's along with some of the others to see which one works best for you and your game.
I don't think you can go wrong with a: Berg, Tactic, Harp, Zone, A3/A4, or Pig. I might be missing a few, but those seem to be the best of the best. Good luck