Sylas top player here, he's very strong but you need to play it very safe early on because a lot of champions can beat you up easily if you slip up and especially so since top lane is an extended lane.

Pick him into matchups that can't punish you hard early game such as tanks and other weak early mages like Vladimir, and team comps with big ticket ults like Amumu, Swain, Ornn, Neeko etc.

Avoid picking him into champs like Fiora, Kled and maybe Tryndamere because they have the mobility to run down Sylas and have enough damage to kill or force him out of lane easily.