It depends on the queries but columnstores would yield a faster result. We're not new to this and have used ClickHouse, MemSQL, SQL Server, and Druid extensively.
Columnstores just store data by column, they do not have any inherent limitations because of it. They all support SQL and compatible tools (although Druid is experimental SQL using apache calcite). They all store columnstore tables on disk (memsql uses rowstores in memory, sql server can optionally run columnstores in-memory using its hekaton engine, and they all use in-memory buffers for rapid ingest). They can all do geospatial queries, support JSON columns and some can handle nested/repeated structures. Indexes are available but unnecessary when you can prune partitions based on what's contained in each segment, especially when using a primary sort key (like a timestamp column in your case). SnappyData has a unique statistical engine to tradeoff query precision for much faster results (like HLL+ algorithms applied to the entire dataset). MemSQL will do OLTP access with full transactions across both rowstore and columnstore data.
Congrats on the VC funding, I'm always happy to see new projects and building on Postgres does give you a solid base with triggers and foreign keys (which come with their own scaling issues), and extending time-based functions will be useful -- however my issue is the marketing spin where you claim to be better than everything else. Columnstores are very fast, efficient, performant, and time as a dimension is not a new challenge. That's before considering the bigquery/snowflake superscale options or specialized databases like kdb+ which have served the financial industry for decades.
Approaching the field with a single-node automatic partitioning extension (as of today) for a rowstore RDMS and saying you're better than the rest on features that they already have just strikes me as insincere. It would be better to recognize the competition and focus on what you're good at instead.