In one video I've seen UTM used mouse emulation without absolute positioning: it treated the screen surface as a giant trackpoint nub and you could move away from the current location with variable speed. A native on-screen keyboard is also available.

For absolute positioning a USB input device is emulated, so this might not work in Windows 98 without a suitable driver: https://docs.getutm.app/preferences/ios/#cursor

Win98 does work with absolute USB mouse input. VirtualBox uses it by default.