https://sqlite.org/limits.html15.Maximum Number Of Tables In A Schema
Each table and index requires at least one page in the database file. An "index" in the previous sentence means an index created explicitly using a CREATE INDEX statement or implicit indices created by UNIQUE and PRIMARY KEY constraints. Since the maximum number of pages in a database file is 2147483646 (a little over 2 billion) this is also then an upper bound on the number of tables and indices in a schema.
Whenever a database is opened, the entire schema is scanned and parsed and a parse tree for the schema is held in memory. That means that database connection startup time and initial memory usage is proportional to the size of the schema.