any idea on what is the max. size of DB percona PXC 8.0.19 can handle ?
No limit. You are only limited by your filesystem and network speeds.
Not even a limit over terabytes ?
e.g. MS SQL server:
Maximum capacity specifications for SQL Server - SQL Server
Database size: 524,272 terabytes
MySQL has no limit on the number of databases. The underlying file system may have a limit on the number of directories.
MySQL has no limit on the number of tables. The underlying file system may have a limit on the number of files that represent tables. Individual storage engines may impose engine-specific constraints. InnoDB permits up to 4 billion tables.
The effective maximum table size for MySQL databases is usually determined by operating system constraints on file sizes, not by MySQL internal limits.