I have an elasticsearch setup with 192 active indices ranging from a few hundred mb to possibly 5gb each. I read that for a logstash use case with 1gb indices you should only use 1 shard. The difference with my setup is that I will be having more users (estimate of up to 100) expecting a quick response time. I intend to have 1 replica for reliability.
Will having 1 shard per index still be appropriate for my use case?
In a word: yes.
The need to create multiple primary shards derives from the need to isolate documents, extreme counts (e.g., when you're in the billions of documents volume), or to improve write throughput (write documents across more places, thereby reducing individual burden).
In practice, you want to shard based on your use case, unless you're one of those first two scenarios (isolation or extreme counts).
If you're read heavy, as most use cases are, then having fewer shards will help you by limiting the request size (fewer places to look). Given that your shard sizes are also relatively small (I'd consider anything under 5 GB to be relatively small), you can easily get away with having a single primary shard and it should benefit your search performance by doing so.
Indexes that share the same mappings, but are also tiny ("few hundred MBs"), should likely be combined if you search across them. If they're independent, then it really makes no difference and the isolation sounds like good practice at the expense of slightly bloating your cluster state (with each index).