This a collection of all tips that I have discovered so far:

Hold jump: Almost all characters will jump higher/farther if you hold the jump button.

Forgivable surfaces: Many surfaces that are at a steep angle will often allow you to still jump normally.

Upon death: turtle: The game might give you a turtle (extremely useful item) when you die. So check for that always. It might cost you 1-4 seconds to look/grab a turtle but it might save you a minute when you need it in a pinch.

turtle abuse: A few times you might have to leave a level to do another level and you would prefer to get right back to the previous level? Well if you just use the turtle inbetween getting the card and loading the next level you will go back a level but you will still have the card. Most useful for "Stare down drums" and "enter bird's dream"(wait until the dream has fully loaded before you use the turtle).

alternate left-right movement: The controls in this game are very floaty and often you will overshoot platforms. Move left-right/forwards-backwards to reduce the floatiness and make more accurate jumps. Holding a direction for a long time during a jump will often result in too much acceleration and death.

Hidden access to the red fly level: When you touch the blue bird sprite you will fall down. Land left of the crocodile and move into the tree. This will result in a quick mini-game (2-3 sec) after which you are in the red fly level.

Quickest access to the key level: You will need to go the key level 3 times to deliver the gold, blue, and red key. Here are the quickest routes from each major hub(not measured yet): Evaporation: Get TP or Rain. TP: Shoot the top right target (green insect level) and when playing the FPS, shoot the middle and left switch. Then go into the level on the far right and in that level jump down. Rain: Go into the tall building with yellow marks. In the dizzy labyrinth touch the ice cream man painting. In the ice cream man level jump down.

You don't have to do all levels!: This is obvious if you consult the "Every single card" doc but it bears repeating. There are many levels that don't have any cards in them.

Memorize the optimal routes beforehand: During the game there will be only 3 moments where you will have a break (when you deliver the 100/200/500 collectibles). So make sure that you don't have to look at notes too much during serious runs as death comes very quickly.

Do areas together: This is more subjective but I find it easier to do all TP levels(levels that are accessed from the TP and loop back into it) together for example. This makes it easier to remember which of the 86 cards you got so far as you can just cross of an entire area.