Using Redis as the cache store in AWS ElastiCache with a Rails 5.2 app

Im using Redis in AWS ElastiCache as the cache store for our Rails 5.2 app. I have the following two questions:

1. We are using SSL in AWS ElastiCache and the redis-rb gem (https://github.com/redis/redis-rb) in the Rails app. The hiredis driver for Redis in redis-rb currently does not support SSL because of which we have to use the default ruby driver. I know that hiredis is overall faster than the default ruby driver, but will using the default ruby driver cause any significant performance issues given that our app receives a large volume of traffic ?

2. Is Rails.cache thread safe if i decide to use the connection_pool gem (https://github.com/mperham/connection_pool.git) for using connection pooling with Redis ?