Is this heavy on UPS?

No. It avoids an always-on per-tick player loop. Refresh work only runs while a supported filter GUI is open, and heavier context scans are throttled separately.

Does this replace vanilla behavior?

No. It adds helper buttons beside existing vanilla GUIs. Filters, splitter filters and logistic requests are still normal Factorio state.

Is this safe for existing saves?

Yes. It can be added or removed safely. Removing it only removes the helper GUI and settings, not vanilla filters already set on entities.

Which Factorio version is this for?

Release 2.0.0 is for Factorio 2.0.

Does this require Space Age?

No. Space Age is optional. If Space Age or Quality is present, item qualities are preserved where the Factorio API supports them.

Does it work with other mods?

It should work with normal modded filter slots, filtered inventories, belts, recipes and fuel categories. Very custom entities may need a compatibility pass if they expose filters through non-standard runtime APIs.