Sorry for the late answer (it seems I’m the only Switch speedrunner here 😅).
Switch version can be tricky: I had in the past encounter some glitches due to old version of the game (in PC version, they did update and patched most of those exploits) but it doesn’t affect the speedrun (just annoying if it happens, like a sudden green screen). I’m playing with a 8BitDo Lite Controller, but JoyCons are okay (if you’re not affected by its button size): playing left AND right can be a way to be consistent, but don’t spam alternatively between hands -> better is to spam a direction with one button. ProController may have long travel press buttons (so not fit to spam in a tempo maybe?), it’s DPad is not ideal, sticks for speedrun vectronom is janky.
Input sensitivity? Don’t understand. The player input margin must be at default (speedrun rules) because it’s affect the detection time intervals of the inputs. It don’t affect inputs of the controller.
Speedrun wise: look out for the other speedruns for inspiration and fastest strats. Some strats are very difficult: there are always easier strats that are safer and more consistent at all levels. Maybe go in the game’s Discord for more tips? 😉
Yeah that can be applied to other levels: you have to be running n the lower-spikes at a constant "triplet"-like tempo. This running off-checks with triplet timing (the game check 4 times every beat the hitboxes) works also with disappearing/moving floor-squares. Great use case of this strat: Arrow2, Waltz3, Autobahn (very hard), Diamond1/2 (very hard run over spikes), CheckerWaltz3, ShipHop2 (lots of strats/speed to try).
That off-beat can be applied to dodge moving ground-spikes: Concentric2 (look at my blindfolded run 😉).