1. Absolutely. clickhouse-keeper is distributed as a standalone static binary or .deb package or .rpm package. You can use it without clickhouse as ZooKeeper replacement.
2. It's not recommended to use slow storage devices for logs in any coordination system (zookeeper, clickhouse-keeper, etcd and so on). Good setup will be small fast SSD/EBS disk for fresh logs and old logs + snapshots offloaded to S3. In such setup the amount of PUT requests will be tiny and latency will be as good as possible.