As the first Kirby game ever, this game doesn't have any copy abilities. The movement is relatively simple compared to most other mainline Kirby games, but there are still some mechanics that are worth pointing out.
Jumping
Like other Kirby games, jumping is a better option than floating for upward movement, unless the latter is required. Unlike some later games in the series, jumping itself doesn't provide a speed boost compared to walking - in other words, bunny hopping doesn't exist in this game.
TAS Spit
Initially having been used in TAS runs in the mid-2000s, it was found to be RTA-viable as well around 2018. This glitch will enable Kirby to instantly exhale the next object he inhales. A TAS spit can be primed by swallowing an object, pressing right or left and down quickly after exhaling an object, or entering a door while floating. After the TAS spit is primed, Kirby can instantly exhale objects as long as he gets close before inhaling them, and will even exhale the first enemy automatically if there are multiple enemies within his inhale range. TAS spits are helpful to save small amounts of time in some boss fights and can save notably more time by enabling double hits on King Dedede. TAS spits also enable doing double hits in the Kracko fight in Extra Mode (the TAS is even able to do a triple hit by hitting all 3 bombs in 1 cycle and can also do a double hit on Kracko Jr.)
Dedede Double Hits
After priming a TAS spit, when Dedede does his jump attack, Kirby can stand to one side of where he will land and jump, then start moving towards Dedede and inhaling around the time the stars appear. This will cause one star to instantly shoot out and hit Dedede while Kirby stores the other one and can use it to do damage as well, and can even prime another TAS spit when exhaling that star. It's even possible to do Dedede double hits damageless if Kirby is positioned precisely enough. Right or left must still be tapped in order to do the TAS spit, but they must be let go of immediately for Kirby to not collide with Dedede. For a video explanation, watch Speedman's guide here.
Inhale Cancelling
During the inhale, pressing up instead of letting go of B ends the inhale sooner. This doesn't save time on its own but it's a useful trick for RNG manipulation runs as inhale advances RNG multiple times quickly.
Lag Reduction & Damage Boosting
Like many older games, when too many sprites appear in the same screen, it can create significant lag. Runners try to eliminate certain enemies to keep the game running smoothly, sometimes even by damage boosting. Usually it is equally fast compared to walking. It saves notably more time, however, if there is a door or a warpstar at the end of the boost.