I always liked watching platformers being speedrun but I don’t know what exactly to speedrun. I want game that don’t have many frame perfect techniques or glitches. So any suggestions would be good.

I have a perfect one for you in mind. It's a free, very simple, and short platformer called Super Blue Boy Planet https://store.steampowered.com/app/560260/Super_Blue_Boy_Planet/

Ooh, something I can help with! I will just go and assume that you meant "2d side-scrolling platformers", because that is basically almost all games I'm running.

Now, what you "want to speedrun" varies on the subgenre of games you like to play, and the expected time range for the runs. I don't know anything about your preferences, so I will write a list with a few examples, and you can tell us your preferences for better suggestions. I will focus on web games, but you can find countless similar examples for PC and consoles.

• Short puzzle/action games - games with a lot of very short levels, with one special concept used across the game; or just one but very short level. A casual playthrough might take some time for the player to figure what to do; but when speedrunning, the puzzle aspect is thrown away and it's pure action. Every level can take a few seconds at most. There also might be frame perfect techniques, but it's really depends on the game itself. Runs in those games usually take 2-5 minutes. For example, one of the popular games is Choppy Orc. Other examples: Overlords New Mansion, Doodle Alive, Hat Wizard, A Platformer for Ants.

• Longer puzzle/action platformers - Same thing, but runs take 10 minutes or more. They have much more short levels, or few but long levels (which can sometimes take minutes to complete). Running games like that requires a bit different mindset than the short ones. Examples: BLYM, Continuity, Skullface.

• Metroidvania/adventure platformers - Games with usually one giant map. You gradually gain access to more areas and upgrades as you progress. You may or may not fight enemies and bosses in the process. Examples: Robot Wants series, Arzea, Snailiad, K.O.L.M, Endeavor, Amidst the Sky, Temple of the Four Serpents.

• Action precision platformers - Where you usually have lot of enemies, spikes and hazards. You don't have the ability to fight, and need to dodge everything while proceeding through the levels. Runs in those games are usually heavily input-based, though. Examples: Meat Boy, Mr. Bree, Exit Path, Give Up, Vex, Jumphobia, Moneyseize.

• Shooting arenas - Games with much heavier focus on shooting, and not on the platforming. You need to shoot and kill enemies in order to progress. Still 2d side-scrolling games, though. Examples: Raze 2, Strike Force Heroes.

I might have missed a few subgenres along the way.