I am a league player who started back in season 4, quitted at season 5, and came back during 2020 since covid locked us in our houses. I have been at top 200 in my server with kayle, and playing the game mostly for trying out new builds. I seldomly stream, feel free to drop by if you find me streaming, I can try out off meta builds you suggest on my stream as well, and would be glad to discuss new strategies. I sometimes stream on twitch you can come by to say hi, also you can simply ask for me to try any build, and I will if it seems reasonable.

Pros:

You are kayle, the ultimate late game carry. If game goes long enough no one can stop you.

You have a heal rivaling most healers except maybe soraka and yuumi, but your damage compensates for it.

Your enemies won't expect you to be on support, and most won't have prior experience with the matchup, so you will have the element of surprise.

Your ultimate makes your allies literally immune to almost all kinds of damage including true damage, for up to 3 seconds. 3 seconds means morgana q, so yeah, it is a long time for a teamfight scenario.

You can push sidelanes mid/late game if you have proper vision control, if you have time to prepare yourself, you can run away pretty easily with q slow and w speedup

If you happen to have a level 1 fight, just remember that kayle is designed as a top laner. Her level 1 is surprisingly strong if you land q to decrease their resists.

Cons:

You are squishy.

You need to rely on your adc until you get level 6, since you can't do that much pre 6.

Your damage output won't be huge until you stack some items, and even when you get that, your damage will mostly be on your 5 stack passive until level 16.

You are playing off meta, so prepare to be flamed down to hell if you happen to lose.

Laning with kayle is not that easy on top lane, but while you are playing as a support, you don't need to worry about getting last hits on creeps pre 6. Focus on poking enemies whenever you can with your q, but don't all in. Your w has a high mana cost and does not provide enough heal in the early game, save it for escapes mostly or time it so your aery shield compensates for the lack of early heal. After you hit level 6, you can poke pretty safely with ranged attacks and get support item gold. Aiding your jungler during a gank is pretty easy too, speed them up with w, slow enemies with q and you can catch up in no time, just like top kayle, you benefit a lot from ganks while your jungler can also get some easy kills and snowball off of it.

Around mid game, you get some healing and if you get imperial mandate, you get an above average poke damage for a healer. Focus on landing q's and only use r if your carry is jumped on. If you had a good laning phase, mid game should be easier, just watch out for assassins. If you need levels, get some camps from jungle and maybe get some minions under your own turret from side lanes, you are not getting them for gold anyways so don't worry about support minion rule.

Well That's where you shine the most. You don't have the damage of solo kayle sure, but you get lots of heal and utility for your teammates it is almost certain for you to win if the game reaches to that stage. just don't forget that you are most likely still squishy, and you should be good to go.

You need to manage your mana early on, try to poke with your e since it helps you to stack manaflow, getting that max stack on the rune is pretty good for mana sustain.

You can extend the range of your q using minions, and also the hitbox extends a litte bit sideways after collision, if the enemy frontline clumps in a straight line, aim for the middle and you can shred resists on multiple targets.

I will update the guide, since it got more attention than I expected. Testing something new right now.