Tiagra 4700 is a 10 speed system with a different cable pull than the rest of the lineup.
GRX is 10 speed, and the 400 series is compatible with Tiagra 4700.
Tiagra RD-4700 rear derailleurs have a short cage (SS 28T) and medium cage (GS 34T). You can use the GRX RD-RX400 rear derailleur with Tiagra ST-4700 shifters to run a 36T cassette. The GRX has a Shadow+ clutch for better offroad performance.
Tiagra 4700 front derailleur is a better fit for road frames and chainrings up to 52T.
The GRX FD-RX400 front derailleur is 2.5mm further out, designed for the 46-30T GRX FC-RX600 crankset. Use this combination for a frame with a boost chainline.
Speed
Shifter variations