which aura/information perk is the best? BBQ? TT?

My personal opinion is that BBQ is the best solely for the bloodpoints. That's the main reason I use it, as it'll still help you consistently earn more points even if a better perk might allow you to 4K every game.

Ultimately it just depends on a lot of things - what killer you're playing, what the survivors do, etc. There's way too many factors to determine one as the "best" perk. You've already put a lot of thought into the ups and downs on each perk, so next is determining what fits your playstyle best, as well as what synergies you want to use.

BBQ slots into any build, and is the best general-use aura perk. It gives free value as long as you can get hooks. It's best on mobile killers that can capitalize on distant auras after hooking: Nurse, Hillbilly, Spirit, Freddy, and Oni come to mind. The downside to BBQ is in its common usage. People have learned how to counter it and understand how it works.

I'm not a huge fan of Thrilling Tremors myself precisely for the reasons you already mentioned: the info it gives can be misleading if survivors get off the gen, and it's a perk that can be identified by watching generators on pickup. After that, it simply becomes a matter of deciding if you want to wait the block timer out.

Discordance can be risky, because survivors are already most efficient when they spread out. However, it gives you value by letting you pressure multiple survivors at once, and gives you a heads-up on gens that might otherwise be completed quickly. Use it for mobile killers (see: BBQ) and killers that benefit from survivors that group up (Plague and Legion).

Surveillance is great with Ruin. Even if the totem stays up for no more than a minute or two, the amount of map knowledge you get from paying attention to which gens aren't highlighted in white can help you decide which areas to prioritize. It's also good for a defensive playstyle, so it can work for Freddy, Hag, and Doctor.

Nurse's Calling can be good for killers that can get close to survivors quickly once noticed, and it combos well with anti-healing perks, specifically Sloppy Butcher. That increases the chance that you'll see their aura while healing. Nurse's Calling is very good on stealth killers (Pig, Myers, Ghost Face) and killers that can close small gaps quickly (Nurse, Huntress). The problem with Nurse's is that it doesn't consistently keep up pressure after a hook, and can also be reliant on survivors grouping up to spread out hits, but getting that kind of pressure is underrated and can completely swing a game when it does happen.

I may have left something out or forgotten something, but I hope this helps! In the end, it comes down to personal preference.

My favourite is the combo Pop + Surveillance. If you can spot a 3 or 4 gen situation early in the game, then it is the best perk to keep these gens up. If you know the gen is low you know you can comit to a chase, you just need to remember which gen just turned yellow. And if you know there are more than one survivor around, spread the damage and follow the second one. Any further progress during the chase can be reverted with pop

bbq works best for me. I might use thrilling tremors on legion once in a while. I don't like 1 minute cooldown on it and doesn't work well with gen regression and pgtw. Plus if nobody is on the gen you get nothing from it

bbq is just so so so good you hook near the edge and see everyone and if you cant see them you now they are close plus its just double mountain dew exp every day with it