1) 1 top 1 jungle 1 mid 2 bot is the meta, but the champion type can vary greatly in nearly every role. ADC can be in bot mid and some in jungle for example.

2) It's kinda scripted if you want compared to dota, especially in the early game when it's most likely that all lanes either farm or have a quick 4man turret takedown strat that's not used that much anymore in pro play. You only see variance later depending on the team comp with either split pushing, singeing....etc

3) Lately many new champions have been introduced with new unique mechanics and some old ones had very unique playstyles too but again, if we compare to dota then yes it might feel not that powerful since Riot's policy over the last few years became against hard carrying as 1 champion.

Some unique champion examples (some are old and had abilities/ qol changes), also note that not all while they are somewhat unique not all champions are used in the meta.

• Singed : You basically fight by running around.

• Nocturne : Great ultimate that denies vision globally and is a long range leap

• Aurelion Sol : Has a skillshot that grows larger and larger the more you travel while you stay in range, also his passive is 3 bolts that turn constantly around you and damage enemies on contact at not cost.

• Rek'Sai : an ability that gives you limited vision but allows you and the whole team to sense enemies that are out of vision/ stealthed at a long range (think sonar ability)

Camille : Passive that procs you 2 types of shields based on the enemy you attack (attacking an AP type champ gives you shield against ap damage and agaisnt AD damage when attacking AD champs), also has a wall bounce skillshot/gapcloser.

As far as ability uniqueness and playstyle that revolves around them, lol has those but then again you wont find anything extremely powerful for the reasons stated above.