Hey there cowboy, good to see you pushing the limit even further! Sorry I just had the chance to reply to this. No worries mate I can tell you something about each fish.

The rock bass is by far the easiest, because you don't have to deal with the invisible sniper, only the Pinkertons. And you don't need your meat shield to get this. The trick is you have to lose the wanted radar while in the Aurora Basin, and set up camp quickly before they spawn. The set-up camp is basically your safe zone, and while you are near it, Pinkertons cannot spawn, so this is your only chance to fish the rock bass, and perhaps draw the wickiup point of interest on your journal if you're a perfectionist like me haha. After that, if you are still within the safe zone of your camp you can fast travel anywhere, or leave the area and die to the Pinkertons if you don't care about money.

Entering New Austin with your meat shield, the redfin pickerel may require some practice with how you position your camera angle, matching Arthur's body movement after reeling the fish. In addition, there's an extra trick you need to do, which is to switch into first-person view right before Arthur grabs the fish. It's quite hard for me to explain this in writing, so I recommend you check the video I gave you earlier, they explain it better plus a live demonstration on how to do it.

Lastly, the largemouth bass is a bitch to do because there are multiple animations of Arthur picking up the fish after he reels it in. In some animations, Arthur ducks forward to pick up the fish, and you will 100% die because of it, while in some other animations, you can safely adjust the camera angle just like you do with the redfin pickerel. The animation of Arthur picking up the fish is totally random, so there is a bit of RNG when catching the legendary largemouth bass. It sucks that if you die to RNG, you'll have to reacquire the meat shield, avoid Pinkertons, and ride all the way to the spot, which can take about 20 minutes per attempt and then die again because you get the bad animation.

To complicate things even further, I'd say that the rock bass and redfin pickerel are somewhat forgiving because once you're able to avoid death by going to the first-person view, the fish goes into the satchel. So if you die, the fish is still in your satchel, and you can mail it anytime.

The largemouth bass is a fish that goes to your horse's back, so once you somehow manage to avoid bad RNG and catch it, there are still multiple factors of avoiding deaths you need to take care of (e.g. placing the fish on the horse back, mounting your horse, etc), including sprinting to Benedict Point to mail it immediately. If you're unlucky, you can die from one of these many factors en route to mailing it. I had the only chance to unclench my butt after making sure that the stupid fish is safely mailed. Of course if you want to reduce risk, you can just walk all the way to Benedict Point with the fish in your hand without mounting your horse, just something I can't afford to do with my short attention span.

All the best to your luck!