There is ABSOLUTELY no reason to use 8.6 client.
You can use all the new outfits, with all the new mounts, and all the new features, and disable anything you don't like.
Don't like mounts? Disable them.
Don't like the new cooldowns? Disable them.
Don't like the skull system? Disable it.
Using 8.6 client is ONLY if you want elfbot to be used by every person that plays your server.
Like Deathzot for example. They WANT players to use elfbot, so they stay 8.6.
So you have 3 choices.
Tibia Client 8.6 - Do you want botters? If yes, use this client.
Tibia Client Newest Version - Do you want to use normal tibia client with as many features as possible? Use this client.
OtClient - Do you want the ability to customize your client? Use this client.